JavaScript

JavaScript Tutorial

Why Study JavaScript?

JavaScript is one of the 3 languages all web developers must learn:

   1. HTML to define the content of web pages

   2. CSS to specify the layout of web pages

   3. JavaScript to program the behavior of web pages

This tutorial is about JavaScript, and how JavaScript works with HTML and CSS.

Did You Know?

JavaScript and Java are completely different languages, both in concept and design.

JavaScript was invented by Brendan Eich in 1995, and became an ECMA standard in 1997.
ECMA-262 is the official name of the standard. ECMAScript is the official name of the language.

You can read more about the different JavaScript versions in the chapter JS Versions.

Learning Speed

In this tutorial, the learning speed is your choice.

Everything is up to you.

If you are struggling, take a break, or reread the material.

Always make sure you understand all the "Try-it-Yourself" examples.

JavaScript References

W3Schools maintains a complete JavaScript reference, including all HTML and browser objects.

The reference contains examples for all properties and methods, and is continuously updated according to the latest web standards.

Complete JavaScript Reference

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JavaScript Quiz Test

Test your JavaScript skills at W3Schools!

Start JavaScript Quiz!

JavaScript Introduction

This section contains some examples of what JavaScript can do.

JavaScript Can Change HTML Content

One of many JavaScript HTML methods is getElementById().

This example uses the method to "find" an HTML element (with id="demo") and changes the element content (innerHTML) to "Hello JavaScript":

Example

document.getElementById("demo").innerHTML = "Hello JavaScript";

Try it Yourself »

JavaScript accepts both double and single quotes: 

Example

document.getElementById('demo').innerHTML = 'Hello JavaScript';

Try it Yourself »

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JavaScript Can Change HTML Attributes

This example changes an HTML image by changing the src (source) attribute of an tag:

The Light Bulb

  

Try it Yourself »

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JavaScript Can Change HTML Styles (CSS)

Changing the style of an HTML element, is a variant of changing an HTML attribute:

Example

document.getElementById("demo").style.fontSize = "35px";
or
document.getElementById('demo').style.fontSize = '35px';

Try it Yourself »

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JavaScript Can Hide HTML Elements

Hiding HTML elements can be done by changing the display style:

Example

document.getElementById("demo").style.display = "none";
or
document.getElementById('demo').style.display = 'none';

Try it Yourself »

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JavaScript Can Show HTML Elements

Changing the style of an HTML element, is a variant of changing an HTML attribute:

Example

document.getElementById("demo").style.fontSize = "35px";
or
document.getElementById('demo').style.fontSize = '35px';

Try it Yourself »

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JavaScript Can Hide HTML Elements

Hiding HTML elements can be done by changing the display style:

Example

document.getElementById("demo").style.display = "none";
or
document.getElementById('demo').style.display = 'none';

Try it Yourself »

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JavaScript Can Show HTML Elements

Showing hidden HTML elements can also be done by changing the display style:

Example

document.getElementById("demo").style.display = "block";
or
document.getElementById('demo').style.display = 'block';

Try it Yourself »

JavaScript Where To

The tags.

Example

<script>
document.getElementById("demo").innerHTML = "My First JavaScript";</script>

Try it Yourself »

Old JavaScript examples may use a type attribute: