Jyrone Parker

Adding Javascript To About Me Page

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Making About Me Interactive

If you have been following this series thus far then you should have an About Me page that looks similar to the following:

About Me Page Pre Javascript
About Me page before javascript implementation

So far we have added the HTML, integrated Bootstrap and added some custom CSS. This blog will serve as an introduction to Javascript. Javascript is the programmig language of the web. HTML defines the content, CSS defines the layout, Javascript defines the behavior. In this tutorial I will introduce you to the high level concepts of Javascript with fine tuned examples later to come.

Random Color Generator

To get you started on the basics of Javascript I will take you through creating a random color generator that will change the background color. This process will require adding a new button to the HTML as well as a new tag <script>. It will also involve an external script that contains the logic for changing the color. Below your phone number add the following HTML

<button id="color-change" class="btn btn-default">Change Background Color</button>

Nothing special the javascript will use this button later. Now create a new folder, call it js/ and inside create a new file called main.js. Inside this newly created file add the following contents.

window.onload = function(){
  document.getElementById('color-change').onclick = function(){
    /* In HTML colors are represented in a 6-digit hexadecimal string
    The values range from 0-9 and A-F*/
    var letters = '0123456789ABCDEF';
    //Colors in HTML are always prepended with a #
    var color = '#';
    //Loop 6 times and randomly select a character from the letters variable
    //Then concatanate to the color string
    for (var i = 0; i < 6; i++ ) {
        color += letters[Math.floor(Math.random() * 16)];
    }
    //set the background color of <body> to the random color
    document.body.style.backgroundColor = color;
  };
};

I’m going to break this down top to bottom:

  • window.onload – The window object represents an open window in a browser, onload is a javascript event that runs the specified function once everything on the page loads.
  • function() – A JavaScript function is a block of code designed to perform a particular task.
  • document.getElementById(‘color-change’)- get the button we just created based on it’s ID
  • .onclick = function(){ – onClick is a Javascript event that fires when an element is *WAIT FOR IT…..* CLICKED!
  • var letters = ‘0123456789ABCDEF’; – a variable called letters that holds all the possible values for a HTML color string
  • var color = ‘#’; – In HTML color strings always start with # followed by 6 characters. Here we initialize a color string.
  • for (var i = 0; i < 6; i++ ) { – A Javascript loop that runs 6 times and evaluates everything between {}
  • color += letters[Math.floor(Math.random() * 16)]; – Remember that color string and letters string? Here we add (concatenate) onto
    the color string and select a random character from the letters string
  • document.body.style.backgroundColor = color; – Set the background color of <body> to the newly generated color.

Your page should look similar to this:

About Me Page Newly Added Button
About Me Page Newly Added Button

If you click the button your background should change to a random color like so:

About Me Page Random Color
About Me Page Random Color

Conclusion

I know it isn’t terribly fancy but you just wrote your first web app! It’s not that difficult is it?! Continuing forth I will add more advanced features to teach more in-depth skills. If you haven’t already please subscribe to my blog via email and feel free to leave any comments below!

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