Month: February 2018

Simple PHP7, SQLite3, and AJAX Tutorial

Simple PHP7, SQLite3, and AJAX Tutorial

Ajax and PHP
Ajax and PHP

    Using PHP and AJAX can be somewhat confusing. But, the benefits are countless when it comes to doing web related projects. So, I wanted to do a simple tutorial/example of how to get things setup and how to do some basic insert and retrieval of data. For this project, I’m using PHP7, SQLite3, AJAX, Firefox, and Atom. You can use any browser with debugging options and any integrated development environment (IDE) or text editor you want. I choose SQLite3 as my database because it’s lightweight and good for applications that need a database.


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Setup

Creating The Layout & Files

Ultimately, my file and directory layout looks like this:

├── ajaxNphp  // This is my working dir
   ├── index.html
   ├── process.php
   └── resources
       └── server.db

The ajaxNphp folder is the root folder of this project. In this folder, we have a resources folder that holds the database and can hold CSS and JavaScript files among other stuff. ***Note: For this project, JavaScript and CSS are inline to the files! I’m trying to keep this as simple as possible.*** For this part, I recommend using the terminal since it can be faster and we will use it for some other stuff during this project. So, KEEP IT UP! Anyway, My project is located in my Downloads folder under the ajaxNphp folder.
So, I open a terminal and type:

cd ~/Downloads/ajaxNphp/

The tilda (~) means your home folder and the rest is pretty self explanatory. I then do:

mkdir resources && touch index.html process.php

This creates the resources directory where our database will go; if successful, it will then create our PHP and HTML files that we will use for the project. The next part is for us to actually install the tools so we can setup our database and start writing code.

The Tools

    I’m using an Ubuntu based operating system so I’ll show the commands you need to get PHP7, SQLite3, and Firefox installed.

sudo apt-get install sqlite3 php-sqlite3 php firefox

OK, now let’s just check that we have the proper versions installed.

PHP Check

// This will somewhat cleanup the version info on retrieval
php -v | awk '{ print $1 $2 }' | head -n1
// I get PHP7.0.25-0ubuntu0.16.04.1 which is PHP 7.0.25, so I'm set.

SQLite Check

sqlite -version
// I get 2.8.17

// If you do too, try:
sqlite3 -version
// If you get a return, then you are set for SQLite3.
// I get a return value so am set.

Ok, so now we need to determine an environment to work with. I recommend Atom because it has a robust set of plugins and themes that make it more pleasant to work with. You’ll need to get it through their website if you wish to use the same thing; but, any text editor will suit this project.

Setup The Database

    OK, so we now need to setup a database that we can query and insert to by using AJAX, PHP7, and SQLite3. I hope you’ve kept your terminal open as we will now change directory (cd) into the resources directory and launch SQLite3. So, here is what we do:

cd resources/ && sqlite3 server.db

We will then be presented with:

SQLite version <Your SQLite3 Version>
Enter ".help" for usage hints.
sqlite>

If you are seeing this, then let’s go ahead and create our database. I setup three columns for this project and they are title, date, and link. Recall, I’m doing a movies database so the first is for movie titles. The second is for when it was released, and the third is the cover image. So let’s create the table in our database.
Simply do:

CREATE TABLE Movies(title MAX, date varchar(10), link MAX);

If it was successful, you should see NO ERRORS and if you run :

.tables

you’ll get it returned. MAX means that the field can take the largest string possible. The varchar(10) means the field is limited to ten characters. There are other data types such as ints, but we will ignore them for now. Now, let’s insert some initial movie data by doing these below commands one at a time. Make sure there is an ending semi-colon for each!

// Date is in MM/DD/YYYY format

INSERT INTO Movies VALUES('Alien', '05/25/1979', 'https://images-na.ssl-images-amazon.com/images/I/61ujvw4OXNL._SX342_.jpg');

INSERT INTO Movies VALUES('Contact', '07/11/1997', 'http://www.filmsgraded.com/posters/01/1/8/8/84a.jpg');

INSERT INTO Movies VALUES('Paul', '03/18/2011', 'https://upload.wikimedia.org/wikipedia/en/thumb/9/96/Paul_poster.jpg/215px-Paul_poster.jpg');

// Check your work
SELECT * FROM Movies;
// You should see the data you entered returned.

// If so, then simply exit.
.exit

Excellent! The commands are pretty simple to understand. They even give a hint of what is going on. We use “INSERT INTO” to start the insert process. We reference our “Movies” table we created and then pass “VALUES” which match up with our title, date, link table layout. We end each command with a semi-colon. Next, we need a server to process PHP commands, interpret our form data, retrieve our data, etc.

Setup The Server

    There are many servers out there one can use and there are some servers that are for testing. If you want to see some options, read my post on Quick Test Servers. For this project, I’m using PHP’s built in server used for testing since it will process PHP and our HTML files.
If you’ve kept the terminal up do this:

cd .. && php -S 127.0.0.1:1212

It’s pretty straightforward for what we are doing here. We moved back to the top directory of the project using cd .. since we only moved down one directory, We then use the “php” command with “-S” as a switch to use its server. We give “-S” an argument of “localhost” (127.0.0.1) and a port of 1212. The port needs to be bigger than 1024 since any port lower and equal to that requires sudo to use. It then waits to process requests. We can use ctrl + c to kill the server which can be helpful for when we want to use ctrl + l to clear the terminal screen of any text output and restart. When your project is complete, you can omit the change directory command and just do the PHP et all part. Add an “&” to the command so that the process is persistent even if the terminal closes. Now, we are truly ready to code!

HTML

Our Basic HTML Template

    Let’s start off with a basic HTML template that we will add to shortly:

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <title>Test AJAX/PHP</title>

<script type="text/javascript">
</script>

</head>
<body>

<h2>Save Movie Info</h2>
<form action="process.php" method="post">
    <input type="text" title="Title" placeholder="Title" name="Title" value="">
    <input type="text" title="Date" placeholder="Date" name="Date" value="">
    <input type="text" title="Link" placeholder="Link" name="Link" value="">
    <input type="submit" name="saveInfo" value="Save">
    <button type="reset" value="Reset">Clear</button>
</forn>


<br/><br/>
<h2>Search Movie Info</h2>
<form>
    <input type="text" name="searchField"
           title="Search"
           placeholder="Search..."
           onkeyup="getData(this.value)"/>
</form>
<br/><br/>


<div id="dynDataField"></div>
</body>
</html>

    Let’s break this down. We have two forms with their own input fields. One form is used for saving new movie entries and the other searches the database and gets the data back. The form that saves new movie info has three fields and a submit button. The three fields correspond to the three columns in our database and Movies table. The submit action uses the forms submit action to send our process.php script POST data about the form for processing.

    The search form has one input field and an onkeyup event that calls a function called “getData”. This function has a parameter passed to it of “this.value” which will take the query that one has typed in. AJAX will be used in this instance to get data from the server as we type in a character. We have a div tag with an ID of “dynDataField” that we will reference to insert the returned data from the server. This is our bare bones HTML. But, it is pretty useless. Clicking any of the buttons or typing a search does nothing. So, let’s create an AJAX script to get our already entered data!

AJAX

AJAX Search Script

    At the heart of AJAX, there are 4 core steps for GET and 5 core steps for POST.

  1. Create an XMLHttpRequest object
  2. Setup an onreadystatechange function for the XMLHttpRequest object
  3. Open a connection with the XMLHttpRequest object
  4. With POST: Setup a setRequestHeader with an XMLHttpRequest object
  5. Send the data with an XMLHttpRequest object
    // Step 1: Create object
    var xhttp = new XMLHttpRequest();  // Create the xhttp object
    // Step 2: Setup an onreadystatechange function for the XMLHttpRequest object
    // This is actually run after send is done and the server spits out info.
    xhttp.onreadystatechange = function() {
        // Confirm we have a  successful connection. Then, receive the response info.
        // For PHP it is echo that sends it.
        // Loops seem to cause this to wait which means an array can be traversed
        // and the output could be written as a table, etc.
        if (this.readyState == 4 && this.status == 200) {
            // do something with the returned data
        }
    };
    // Step 3: Open connection
    // More or less, open a connection: @Params POST or GET, path to XML page or php script, set async t/f
    xhttp.open("GET", "process.php", true);
    // Step 4: Send the data and let server process it.
    //         After done processing it, onreadystatechange is triggered.
    xhttp.send();    // Start the process and send GET data


    //      For POST do and add these changes
    //  xhttp.open("POST", "process.php", true);
    // Used in POST to setup data types like JSON, XML, etc... MUST BE DONE AFTER OPEN
    // xhttp.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
    // Example data structure for Sending POST with above RequestHeader. See that this mimics GET 
    // xhttp.send("fname=Henry&lname=Ford");
    // xhttp.sebnd(formData);  // Can use a string variable with formatted data structure instead

The above is the process. Here is what we setup in our scripts tag that’s in the head tag:

function getData(query) {
    if (query == "") {
        document.getElementById("dynDataField").innerHTML = "<p></p>";
        return;
    } else {
         var xhttp = new XMLHttpRequest();  // Create the xhttp object
         var formData = "dbQuery=" + query; // Our query being setup for processing
         // This is actually run after open and send are done
         xhttp.onreadystatechange = function() {
             if (this.readyState == 4 && this.status == 200) {
                 updatePage(this);  // Send the returned data to further process
             }
         };
         xhttp.open("POST", "process.php", true);  // Open the connection
         xhttp.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
         xhttp.send(formData);    // Start the process

    }
}

function updatePage(returnData) {
    // Get the echoed data and insert to div of dynDataField
    document.getElementById("dynDataField").innerHTML = returnData.responseText;
}

OK, so we have two functions here. One is for getting the data and the other inserts the results into our div. Get data checks to see if the input field is empty and if so leaves things as they are. If there is data in the field, it is then inserted into a variable “formData” and tied in with “dbQuery=”. This is what PHP will look at and use to insert into a database query. We then setup a statechange listener to wait for the server to finish processing the search and we send the result to the other function.

    After this setup part, we do the standard open process but use POST instead of GET. Then, we tell the server what kind of data this is. Recall, GET defines it for us but is limited and less secure while POST has more data formats and better security but we have to define it using the setrequestheader. We then send the data in its formatted string to the server for processing. This w3schools link has some more info about each part. In this instance, the PHP script transfers a string back to the requester. Note, we can transfer JSON, XML, and other data. But, a string or “responseText” is good for now.

Alright, all that’s left is to write our PHP script to process the search and our insert to table option.

PHP

Base PHP

    We have three core parts for the PHP project. We want to determine which form sent the POST. We then call one of two functions. One function will search the database. The other function will insert to the database.
Here is the basic setup:

<?php

// Retrieve data
function searchDB($QUERY) {
}

// Save new entry
function saveInfo($TITLE, $DATE, $INFOLINK) {
}

// Determin action
if(isset($_POST['saveInfo'])) {
    saveInfo($_POST["Title"], $_POST["Date"], $_POST["Link"]);
} elseif (isset($_POST['dbQuery'])) {
    searchDB($_POST['dbQuery']);
} else {
    echo "<h2 style='width:100%;background-color:#ff0000;color:#ffffff;text-align:center;'>Error! Illegal Access Method!</h2>";
}

?>

The part of interest here is the the determine action section. This is how we determine which function to call when a form is submitted or an AJAX call is made. If neither call the script, we drop an error and exit the script. We are simply checking if “saveInfo” or “dbQuery” are set. We then call the proper function and pass the data that is sent. Let’s now setup our search function.

Search Function

    As you might have seen, we are calling our search function “searchDB” and we are passing the “dbQuery” value to it.
So let’s see how we connect to the database and return data:

try {
    $serverPDO = new SQLite3('resources/server.db');
    $query = "SELECT * FROM Movies WHERE title LIKE '%" . $QUERY . "%' OR " .
                                         "date LIKE '%" . $QUERY . "%' OR " .
                                         "link LIKE '%" . $QUERY . "%'";
    $result = $serverPDO->query($query);

    while ($row = $result->fetchArray()) {
        echo "<div style='float: left;margin-left: 1em; margin-right: 1em;'>" .
             "<a href=" . $row["link"] ." target='blank'>" .
             "<img style='width:8em; height:10em;' src='" . $row["link"] . "'/></a><br/>" .
             "Title: " . $row["title"] .
             "<br/>Date: " . $row["date"] . "</div>";
    }

    if ($result->fetchArray() == 0) {
        echo "<div style='float:left;width:100%; background-color:pink;color:#ffffff;text-align:center;'>Nothing Found...</div>";
    } else {
        echo "<div style='float:left;margin-top:2em;width:100%; background-color:lightgreen;color:#ffffff;text-align:center;'>Search Completed...</div>";
    }
} catch (Exception $e) {
    echo "<h2 style='width:100%; background-color:ff0000;color:#ffffff;text-align:center;'>Error!</h2><br/>" . $e;
}

Let’s break this down. In our “searchDB” function, we have a try catch block that checks any exception that might occur. Technically, we really should be more specific to what exceptions might occur but for now, this will suffice. We try to create an SQLite3 database object and give it a local path name of “resources/server.db”. This is set to the “serverPDO” variable. We then create a “query” variable of type string that comprises of an SQL command that very broadly makes the database look at he table and see if any field matches the query. Please note, this is a very in-efficient way to do this as it looks at each field and then sees if any part is like the query both in upper, lower, and mixed casing. If we were being efficient, we’d base our queries on the columns and have either multiple input fields for the search with a “submit” button or use other techniques to keep the searches quick. Since this is a small database, performance isn’t poor and we can get away with this in a general context. Take note that the VALUES section is ordered just like we ordered it when we created the table columns.

    Anyway, we then execute the query and get the result set into the “result” variable. This is essentially a 2D array that comprises an array of result objects that then have an array of values for each object. This is why we use the while loop and access the “row” and then any values there in. We assign the values to a string formatted with HTML markup that is then echoed. After that, we echo whether we traversed an arrays by saying the search was or was not found.

    As I understand it, the “onreadystatechange” is triggered after the script is finished. So, all echos are collected by “onreadystatechange” and once the script sends an exit code the “onreadystatechange” sends what was echoed to whatever you setup to collect and parse the data.

Insert Function

    As you can tell, our insert function will take three paramets which are the title, date, and link.

if ($TITLE != "" && $DATE != "" && $INFOLINK != "") {
    try {
        $serverPDO = new SQLite3('resources/server.db');
        $command = "INSERT INTO Movies VALUES('" . $TITLE . "','" . $DATE . "','" . $INFOLINK . "')";
        $serverPDO->exec($command);

        echo "<h2 style='width:100%;background-color:#0000ff;color:#ffffff;text-align:center;'>Inserted to db...</h2><br/>" .
             "Title: " . $TITLE . "<br/>Date: " . $DATE . "<br/>Link: " . $INFOLINK;
    } catch (Exception $e) {
        echo "<h2 style='width:100%; background-color:ff0000;color:#ffffff;text-align:center;'>Error! Database Insert Failed...</h2><br/>" . $e;
    }
} else {
    echo "<h2 style='width:100%; background-color:ff0000;color:#ffffff;text-align:center;'>Error!</h2><br/>" .
         "<h3>A field is empty...</h3>" . $e;
}

Lets break this down. The first parts are pretty much the same as the search function with the exception of execute than query being the command. We also confirm that each field is filled and if not we generate an error HTML markup. We have a try catch block if they are filled. In the try section, we connect to the database. We create a “command” of type string that inserts the sent data from the form. We then echo a success or failure message. Take note that this insert process is not AJAX. Our page will redirect to the process.php file and the file will output HTML. I’m doing it this way to show you two ways of processing data and why AJAX is useful in that we aren’t being redirected. As you can see, it’s a much cleaner user experience to use AJAX and this PHP example shows why. You can change this to AJAX but I will leave that to you to figure out how.

Conclusion

Discussion

    We are DONE! Pat yourself on the back and get a cold beer or favorite beverage. You now have new possibilities available to you since you understand the basic concepts. Let’s do a quick recap and talk about pitfalls and the next steps one should take.

We start off by creating two files and one sub-folder. We then install our needed programs and a development environment. From there, we create our database in the sub-folder and the table in the database. It is important to recall that one of the fields is limited to a string size of 10. Anyway, we then entered some initial data so we could work with it after creating our code. After launching our PHP server, we create our initial HTML markup and talk about what we will do next. Next, we create our AJAX search script that checks against empties and so on. Since the HTML is done, we move on to the PHP. In the PHP, we check what’s sending the request and determine the necessary action from the POST data. We create our two functions and their logic which get called after the initial checks. Once the script exits, our AJAX sees this and we end the data to a function that then inserts the data to a div tag OR we get an HTML output in the case of the data insert form. We then drink our beverage and think about pitfalls and the next project we will do based off the work done here.

Pitfalls

    The first massive pitfall is that we aren’t sanitizing our data. NEVER do a production project without cleaning input data! I skipped it here because I’m lazy and this article would get longer than I want it to. It can be pretty easy to do though since there are libraries out there one can use. You should use a JavaScript library or your own scripts to check the input. I recommend checking through the server too but the JavaScript should get most issues.

    The next pitfall is that we aren’t checking the length of the date field. This can be done through JavaScript too and PHP can cover the process too. So, this would be one of the next steps to do as well as the above input sanitation.

    The next pitfall is that the search function implements a poor query structure. I mentioned this before but we are collating things to keep in mind so I mention it here too.

    I’m sure there are some other things of note but these three are the biggies. Let’s look at what our next steps might be with such a project.

Next Steps

    Here are some next steps to consider.

  • New Projects:
    • Use cookies to create a login system and account control to then access or create users for the database.
    • Use cookies and AJAX to create a tracking system that’ll insert data to the database about links clicked.
    • Create a meta search engine.
    • Create a password manager..
  • Improve Current Project:
    • Sanitize input fields to avoid exploits and future errors.
    • Implement a date field length check.
    • Make a better search system.

Result Images

ajax and php result
ajax and php result
ajax and php result 2
ajax and php result 2
error handling
error handling
error handling 2
error handling 2

db insert
db insert
HTML, CSS, JavaScript Useful Cheat Sheet!

HTML, CSS, JavaScript Useful Cheat Sheet!


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Web Technologies
Web Technologies

    I love web technologies because they provide a quick return on interest (ROI) and for the beginner gives immediate feedback in terms of accomplishment and sense of progress. There are many frameworks that one can use for a web based project but knowing the base elements these frameworks are comprised from is still important. Here is a reference list/cheat sheet of some of the most common HTML tags, CSS, and JavaScript one will likely use. This is great for Web Devs, Web Admins, coders, programmers, and the like.

HTML Tags

    Most HTML tags are setup as open and close tags. This means that most tags are a pare/set and denote where they start and end. The end tag has a forward slash (/) to indicate the tag is the end tag.

<tag>Stuff in tag...</tag>
(open tag)content(/end tag)

<!--Some tags end like this-->
<tag/>

<div>

    Div tags are considered devision tags and are used to section data on a page. CSS will then be used to style the tag by setting its position, setting the background color, setting the text color, etc. Think of the div as a container and your scaffolding for the page. Div tags are block elements.

<p>

    The P tag stands for paragraph tag and this is like a sub container for the div tag. It often holds text but can contain images, links, and other non-block tags. Browsers will automatically add some space (margin) before and after each <p> element. This behavior can be modified with CSS using the margin properties. P tags are block elements.

<span>

    The span tag is pretty much like the div tag. The difference between the two is that div is a block element which puts it on a separate line. A span tag, however, is an inline element, meaning that it can be on a line with other elements.


<img>

    The img tag stands for images. People like images and I like images.

<img src="https://www.itdominator.com/wp-content/uploads/2017/07/wp-cli.jpg" alt="If image doesn't render, this text will show instead." />

<a>

    Anchor tags link to parts on the same page or to new pages entirely. They are essentially links.

<!--To an external page...-->
<a href="http://www.google.com" target="_blank">Google</a>

<!--This will jump to the content that is wrapped with another anchor tag on the same page.-->
<a href="#colors">Colors</a>

<a name="colors">
<p>Colors are cool. The primary colors are red, green, and blue.</p>
</a>

<table>

    Table is a block element that denotes there will be sub elements of th, tr, td. There are others but these are the core parts. Th stands for table header and
is inset within a tr (table row). Tr is table row which makes a row for the table. Td is table data which is like a column and is inset in a table row too.

border-collapse: separate (default):

FirstnameLastname
TomGar
LoisGriffin

border-collapse: collapse:

FirstnameLastname
PeterGriffin
LoisMatt

form

    A form is used to submit data to the server. There are many form objects one can use. Below is a table covering all HTML5 form objects and their code and examples.

ObjectPreview HTML 5 code
Label

<label>Texte</label>
Button

<input type=”button” name=”name” value=”Bouton”>
Image button


<input type=”image” src=”image/bimage.jpg”>
Text field

<input type=”text” name=”text” value=”empty”>
Password

<input type=”password” name=”monpass” value=”12345″>
Date

<input type=”date” name=”date” value=”<?php echo $today?>”>
Date and time

<input type=”datetime” name=”time” value=”<?php echo $now?>”>
Time<time>2013-06-27</time>
Number

<input type=”number” name=”num” value=”12345″>
Color

<input type=”color” name=”color” value=””>
Search input

<input type=”search” name=”” list=”datalist” value=””>
Data
Dix
<data value=”10″>Ten</data>
Check box

<input type=”checkbox” name=”checkbox1″ value=”checkbox”>
Radio group



<label>Choice 1
<input type=”radio” name=”radio1″ value=”radio1″>
</label>
<label>Choice 2
<input type=”radio” name=”radio1″ value=”radio2″>
</label>
Textarea

<textarea name=”textarea”>content</textarea>
Range


<input type=”range” min=”-100″ max=”100″
value=”0″ step=”2″ name=”power” list=”powers”>
<datalist id=”powers”>
<option value=”0″>
<option value=”-30″>
<option value=”30″>
<option value=”+50″>
</datalist>
Data listTo be used with input
<datalist id=”identifier”>
<option value=”1″>
<option value=”2″>
<option value=”3″>
</datalist>
Select

<select name=”select”>
<option>Alpha</option>
<option>Beta</option>
<option>Delta</option>
</select>
Select list

<select name=”select2″ size=”3″>
<option>Alpha</option>
<option>Beta</option>
<option>Delta</option>
</select>
Menu

  • New
  • Open
  • Save
  • <menu type=”context”>
    <li>New</li>
    <li>Open</li>
    <li>Save</li>
    </menu>
    Toolbar

  • <menu type=”toolbar”>
    <li><button type=”button” onclick=”fnew()”>New</button></li>
    <li><button type=”button” onclick=”fopen()”>Open</button></li>
    <li><button type=”button” onclick=”fsave()”>Save</button></li>
    </menu>
    Combo box


    <input type=”text” list=”comboid”>
    <datalist id=”comboid”>
    <option value=”0″>
    <option value=”-30″>
    <option value=”30″>
    <option value=”+50″>
    </datalist>
    File upload

    <input type=”file” name=”file”>
    Image & caption

    Caption

    <figure>
    <img src=”image/image.gif”>
    <figcaption>Caption</figcaption>
    </figure>
    Fieldset
    Title

    …Content…

    <fieldset>
    <legend>Title </legend>

    <p>Content</p>
    </fieldset>
    Output

    <output onforminput=”value = 2 + 2″></output>
    Meter
    12 units
    <meter min=0 max=24 value=12>12 units</meter>
    Progress 0%
    <progress id=”prog” max=100>
    Summary

    Overview
    term
    definition

    <details>
    <summary>
    Presentation
    </summary>
    <dl>
    <dt>term</dt>
    <dd>definition</dd>


    </dl>
    </details>
    Submit button

    <input type=”submit” name=”submit” value=”Submit”>
    Clear/Reset button

    <input type=”reset” name=”clear” value=”Clear”>

    HTML Entities

        HTML entities are used in place of reserved characters in HTML. Characters that are not present on your keyboard can also be replaced by entities as well. The most common are listed in a table below.

    ResultDescriptionEntity NameEntity Number
    non-breaking space&nbsp;&#160;
    <less than&lt;&#60;
    >greater than&gt;&#62;
    &ampersand&amp;&#38;
    double quotation mark&quot;&#34;
    single quotation mark (apostrophe)&apos;&#39;
    ¢cent&cent;&#162;
    £pound&pound;&#163;
    ¥yen&yen;&#165;
    euro&euro;&#8364;
    ©copyright&copy;&#169;
    ®registered trademark&reg;&#174;

    HTML Notes

    Recommended Default HTML Markup Before Content Is Added

    <!DOCTYPE html> <!--Tells a browser its an html page-->
    <html lang="en">
    <head>
      <meta charset="utf-8">  <!--Encoding model-->
      <title>Title seen on its tab</title>
      <link rel="stylesheet" href="/css/master.css"> <!-- Attach CSS through a path -->%MINIFYHTMLf6998115b28cbc73f3243ee67605383d4%</head>
    <body>
    
    <!-- content goes here... -->
    
    
    <script src="resources/scripts/script.js" charset="utf-8"></script>  <!-- Attach Javascript File through path -->
    </body>
    </html>
    

    Block Elements

        In general, HTML elements can be divided into two categories : block level and inline elements. HTML block level elements can appear in the body of an HTML page. It can contain another block level as well as inline elements. By default, block-level elements begin on new lines. Block level elements create larger structures (than inline elements).

    • p
    • h1, h2, h3, h4, h5, h6
    • ol, ul
    • pre
    • address
    • blockquote
    • dl
    • div
    • fieldset
    • form
    • hr
    • noscript
    • table

    Inline Elements

        HTML inline elements can appear in the body of an HTML page. They can contain data and other inline elements. By default, inline elements do not begin on new lines. Inline elements create shorter structures (than block elements).

    • b, big, i, small, tt
    • abbr, acronym, cite, code, dfn, em, kbd, strong, samp, var
    • a, bdo, br, img, map, object, q, script, span, sub, sup
    • button, input, label, select, textarea

    Margins

        Margins are the spacing around an element.

    This span tag has 2em margin set…

    Padding

        Padding is the spacing internal to an element and its “walls”.

    This span tag has 2em padding set…

    CSS

    Examples/Logic

    SelectorExampleExample description
    .class.introSelects all elements with class=”intro”
    #id#firstnameSelects the element with id=”firstname”
    **Selects all elements
    elementpSelects all <p> elements
    element,elementdiv, pSelects all <div> elements and all <p> elements
    element elementdiv pSelects all <p> elements inside <div> elements
    element>elementdiv > pSelects all <p> elements where the parent is a <div> element
    element+elementdiv + pSelects all <p> elements that are placed immediately after <div> elements
    element1~element2p ~ ulSelects every <ul> element that are preceded by a <p> element
    [attribute][target]Selects all elements with a target attribute
    [attribute=value][target=_blank]Selects all elements with target=”_blank”
    [attribute~=value][title~=flower]Selects all elements with a title attribute containing the word “flower”
    [attribute|=value][lang|=en]Selects all elements with a lang attribute value starting with “en”
    [attribute^=value]a[href^=”https”]Selects every <a> element whose href attribute value begins with “https”
    [attribute$=value]a[href$=”.pdf”]Selects every <a> element whose href attribute value ends with “.pdf”
    [attribute*=value]a[href*=”w3schools”]Selects every <a> element whose href attribute value contains the substring “w3schools”
    :activea:activeSelects the active link
    ::afterp::afterInsert something after the content of each <p> element
    ::beforep::beforeInsert something before the content of each <p> element
    :checkedinput:checkedSelects every checked <input> element
    :disabledinput:disabledSelects every disabled <input> element
    :emptyp:emptySelects every <p> element that has no children (including text nodes)
    :enabledinput:enabledSelects every enabled <input> element
    :first-childp:first-childSelects every <p> element that is the first child of its parent
    ::first-letterp::first-letterSelects the first letter of every <p> element
    ::first-linep::first-lineSelects the first line of every <p> element
    ype.asp”>:first-of-typep:first-of-typeSelects every <p> element that is the first <p> element of its parent
    :focusinput:focusSelects the input element which has focus
    :hovera:hoverSelects links on mouse over
    sp”>:in-rangeinput:in-rangeSelects input elements with a value within a specified range
    :invalidinput:invalidSelects all input elements with an invalid value
    :lang(language)p:lang(it)Selects every <p> element with a lang attribute equal to “it” (Italian)
    sp”>:last-childp:last-childSelects every <p> element that is the last child of its parent
    ype.asp”>:last-of-typep:last-of-typeSelects every <p> element that is the last <p> element of its parent
    :linka:linkSelects all unvisited links
    :not(selector):not(p)Selects every element that is not a <p> element
    sp”>:nth-child(n)p:nth-child(2)Selects every <p> element that is the second child of its parent
    hild.asp”>:nth-last-child(n)p:nth-last-child(2)Selects every <p> element that is the second child of its parent, counting from the last child
    f-type.asp”>:nth-last-of-type(n)p:nth-last-of-type(2)Selects every <p> element that is the second <p> element of its parent, counting from the last child
    ype.asp”>:nth-of-type(n)p:nth-of-type(2)Selects every <p> element that is the second <p> element of its parent
    ype.asp”>:only-of-typep:only-of-typeSelects every <p> element that is the only <p> element of its parent
    sp”>:only-childp:only-childSelects every <p> element that is the only child of its parent
    :optionalinput:optionalSelects input elements with no “required” attribute
    ange.asp”>:out-of-rangeinput:out-of-rangeSelects input elements with a value outside a specified range
    sp”>:read-onlyinput:read-onlySelects input elements with the “readonly” attribute specified
    sp”>:read-writeinput:read-writeSelects input elements with the “readonly” attribute NOT specified
    :requiredinput:requiredSelects input elements with the “required” attribute specified
    :root:rootSelects the document’s root element
    ::selection::selectionSelects the portion of an element that is selected by a user
    :target#news:targetSelects the current active #news element (clicked on a URL containing that anchor name)
    :validinput:validSelects all input elements with a valid value
    :visiteda:visitedSelects all visited links

    IDs

        ID selectors are supposed to be unique within the HTML document. When queried with JavaScript it should return a single element but it can return an array/list if the web developer set the document with multiple IDs of the same type. Standards dictate this is poor form if done.

    <!-- The IDs are arbitrary. -->
    
    <div id="left-container"> <!-- Content --> </>
    <div id="middle-container"> <!-- Content --> </>
    <div id="right-container"> <!-- Content --> </>
    

    Classes

        Class selectors don’t have to be unique within the HTML document. When queried with JavaScript it usually returns an array/list.

    <!-- The Class is arbitrary. -->
    
    <div class="book"> <!-- Content --> </>
    <div class="book"> <!-- Content --> </>
    <div class="book"> <!-- Content --> </>
    

    CSS Button Generator Button Generator

        Quickly make buttons…

    Button













    JavaScript

    Get Elements By ID/Class/TagName/CSS Selector

        Getting elements by id, class, and tag among other options is a sizeable chunk of the JavaScripting one will do. This allows us to interact with the DOM

    // Get HTML element(s) with specified id.
      var x = document.getElementById('id');
    
    // Get HTML elements with specified class.
      var x = document.getElementsByClassName('className');
    
    // Get HTML elements with specified tag.
      var x = document.getElementsByTagName('tagName');
    
    // Get HTML elements tht matches a specified CSS selector
    // This example returns a list of all  elements with class="icon".
      var x = document.querySelectorAll("img.icon"); 
    

    Function

        The basic block of coding we all know and have come to love. Yes…the function.

    function sum(a, b) {
        return a + b;      // The function returns the sum of a and b
    }
    var sumVal = sum(2,4);
    alert(sumVal);  // Will pop-up saying 6
    

    If Statement

        Check the conditions.

    if (condition) {
    }
    

    Loops

        Loops baby, they’re needed and these will meet your needs.

    // Standard loop
    for (var i=0; i<array.length; i++) {
       array[i].innerHTML;
    }
    
    // For In Loop
    for (var tag in elements) {
        // Do stuff while there are tags to work on
    }
    
    // While Loop
    while (condition) {
        // Do stuff while condition is met
    }
    
    // Do While
     do {
        // One at least one and keep doing stuff while condition is met
    }
    while (condition);
    

    Switch/Case Statement

        Good for menu stuff, switch/case statements are ready for the job.

    var day;
    switch (new Date().getDay()) {
        case 0:
            day = "Sunday";
            break;
        case 1:
            day = "Monday";
            break;
        case 2:
            day = "Tuesday";
            break;
        case 3:
            day = "Wednesday";
            break;
        case 4:
            day = "Thursday";
            break;
        case 5:
            day = "Friday";
            break;
        case  6:
            day = "Saturday";
    }
    alert(day);
    

    Alert & Console Log

        Error logging is helpful. The two way to do this are through alerts and console logging. Most of the time, alert isn’t used but it can be helpful to warn the user, etc.

    // This will generate a pop-up window with the "Hello, World!" text.
    alert("Hello, World!");
    
    // This will log to the console the "Hello, World!" text.
    To access the console in Firefox, do Ctrl+Shift+J
    console.log("Hello, World!");
    

    Adding Event Listeners

        Event listeners are the next most important after getting an element. They allow us to let the user click on stuff or interact through other ways in order to create dynamic interactions.

    // This attaches a click event to the entire DOM.
    // We can then check which IDs, Classes, etc were clicked to then do other things.
    
    document.addEventListener("click", (e) => {
        if(e.target.id == "alert2")
            alert("You clicked an element with the ID of alert2");
    
    });
    
    
    // This attaches to a specific element with the ID of cars and
    // when clicked alerts us to the innerHTML text.
    
    <p id="cars">Hello, World!</p>
    
    document.getElementById('cars').addEventListener("click", (e) => {
            alert("The content is:  " + e.target.innerHTML);
    });
    
    // This attaches it in a different manner.
    document.getElementById('cars').onclick =  function(){
        // do stuff
    }
    
    // You can add it though a tag as well.
    <div onclick="myFunction()"> I am clickable! </div>
    

    Here is a list of some common HTML event attributes:

    EventDescription
    onchangeAn HTML element has been changed
    onclickThe user clicks an HTML element
    onmouseoverThe user moves the mouse over an HTML element
    onmouseoutThe user moves the mouse away from an HTML element
    onkeydownThe user pushes a keyboard key
    onkeyupThe user releases a keyboard key
    onloadThe browser has finished loading the page

    Arrays

        Arrays in JavaScript are a special object and really act like lists or vectors since we can push new values to it.

    // An empty array
    var cars = [];
    
    // Has nodes/objects
    var cars = ["Toyota", "Sab", "Mazda"];
    
    // Add to array
    cars.push("Nesan');
    
    // Remove from end of array
    cars.pop();
    

    Parent Element

        Sometimes, we need to access the element that contains the element we accessed. This could be because we want to remove the element or we want to add something next to it than in it.

    <div>
        <p id="cars" >
            Cars are cool.
        </p>
    But boats are even more cool.
    </div>
    
    var x = document.getElementById('cars').parentElement;
    alert(x.innerHTML);  // This will present an alert box with "But boats are even more cool."
    
    
    // This will remove the element we accessed from the div
    var childElm = document.getElementById('cars');
    var parentElm = childElm.parentElement;
    
    parentElm.removeChild(childElm);
    

    Cookies

        Sometimes, we need to store user information for later usage. This is where cookies come in.

    function saveAsCookie() {
        var uName = document.getElementsByName("userName")[0].value;
        var eml = document.getElementsByName("email")[0].value;
    
    
        // should set expires date: Ex -> expires=(UTC date).
        // Use secure; in argument to make sure it only transports across HTTPS or secure connections
        document.cookie = "username=" + uName  +"; path=" + document.URL;
        document.cookie = "email=" + eml + "; path=" + document.URL;
    }
    
    function displayCookies() {
        var cookiesField = document.getElementById("cookieField");
        var cookies = document.cookie.split(";");  // Set as an array to traverse....
    
        for (var i=0; i<cookies.length; i++) {
            cookiesField.innerHTML += cookies[i] + "<br/>";
        }
    }
    
    function clerCookies() {
        var expireDate = "Thu, 01 Jan 1970 00:00:00 UTC";
        document.cookie = "username=; expires=" + expireDate;
        document.cookie = "email=; expires= " + expireDate;
    }
    
    <form>
    <input type="text" title="User Name" name="userName" placeholder="User Name" value=""/>
    <input type="text" title="Email" name="email" placeholder="Email" value=""/>
    <input type="button" name="submit"  onclick="saveAsCookie()" value="loginSubmit">
    </form>
    
    <button type="button" name="button" onclick="displayCookies()">Get Cookie</button>
    <button type="button" name="button" onclick="clerCookies()">Clear Cookie</button>
    
    <div id="cookieField"></div>
    

    AJAX

        AJAX is a developer’s dream, because you can:

    • Update a web page without reloading the page
    • Request data from a server – after the page has loaded
    • Receive data from a server – after the page has loaded
    • Send data to a server – in the background
    function loadDoc() {
      var xhttp = new XMLHttpRequest();        // Create the xhttp object
      xhttp.onreadystatechange = function() {  // This is actually run after open and send are done
        if (this.readyState == 4 && this.status == 200) {  // Confirm we have a  successful connection
         // Receive the response info. For PHP it is echo that sends it. Then set into demo div
         document.getElementById("demo").innerHTML = this.responseText;  
        }
      };
      xhttp.open("GET", "ajax_info.txt", true);  // post or get, path to XML page or php script, set async 
      xhttp.send();                              // Start the process
    }
    
    
    <button type="button" name="button" onclick="loadDoc()">Load XML</button>
    <div id="demo">

    String Manipulation

        String Manipulation can be important when handling cookies or data. Sometimes we need to split it into an array, make it lower case or vise versa, find a sub string, or more.
    These should get you started:

    // Find sub string
    var str = "Hello world, welcome to the universe.";
    var n = str.includes("world");
    
    // Find sub string at offset
    var str = "Hello world, welcome to the universe.";
    var n = str.includes("world", 12);
    
    // Replace string 
    var str = "Windows!";
    var res = str.replace("Windows", "Linux");  // old value, new value
    
    // Replace all case sensitive
    var str = "Mr Blue has a blue house and a blue car";
    var res = str.replace(/blue/g, "red");
    
    // Replace all case-insensitive
    var str = "Mr Blue has a blue house and a blue car";
    var res = str.replace(/blue/gi, "red");
    
    // String split
    var str = "How are you doing today?";
    var arry = str.split(" ");  // Split by spaces
    
    // To Upper
    var x = "Linux";
    x.toUpperCase();
    
    // To Lower
    var x = "LINUX";
    x.toLowerCase();
    

    Conclusion

        I think this list is pretty good and fits most user's needs. This should definitely help those who are looking for a certain tag or CSS logic or are just wanting to see a broad selection of what web technologies are based off of. Coders, website developers, Admins, etc should have most of what they need right on the page with good samples to start. Leave a commemt if you'd like me to add something else! Anyway, if you liked this reference sheet/cheat sheet, start using what you have learned by setting up a quick test server! Read my article by clicking the below image!


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