JavaScript

What is JavaScript?

• JavaScript is the programming language of HTML and the Web.
• JavaScript is easy to learn.

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

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":

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:

<onclick="document.getElementById('myImage').src='pic_bulbon.gif'">

JavaScript Can Change HTML Styles (CSS)

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

document.getElementById("demo").style.fontSize = "25px";
or
document.getElementById('demo').style.fontSize = '25px';  

JavaScript Can Hide HTML Elements

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

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

JavaScript Can Show HTML Elements

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

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