- JavaScript is the programming language of HTML and the Web.
- JavaScript is easy to learn.
- This tutorial will teach you JavaScript from basic to advanced.
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.
JavaScript References
W3Schools maintains a complete JavaScript reference, including all HTML DOM, and browser objects.The reference contains examples for all objects, properties, and methods, and is continuously updated according to the latest web standards.
Complete JavaScript Reference
JavaScript Quiz Test
Test your JavaScript skills at W3Schools!Start JavaScript Quiz!
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";
JavaScript Can Change HTML Attributes
This example changes an HTML image by changing the src (source) attribute of an <img> tag:
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 = "25px";
JavaScript Can Hide HTML Elements
Hiding HTML elements can be done by changing the display style:
Example
document.getElementById("demo").style.display="none";
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";
JavaScript Where To
JavaScript can be placed in the <body> and the <head> sections of an HTML page.
The <script> Tag
In HTML, JavaScript code must be inserted between <script> and </script> tags.
Example
<script>
document.getElementById("demo").innerHTML = "My First JavaScript";
</script>
JavaScript Functions and Events
A JavaScript function is a block of JavaScript code, that can be executed when "asked" for.
For example, a function can be executed when an event occurs, like when the user clicks a button.
You will learn much more about functions and events in later chapters.
JavaScript in <head> or <body>
You can place any number of scripts in an HTML document.
Scripts can be placed in the <body>, or in the <head> section of an HTML page, or in both.
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