JavaScript Introduction

This page contains some examples of what JavaScript can do.

JavaScript Can Change HTML Content

One of many JavaScript HTML methods is getElementById().

The example below "finds" an HTML element (with id="demo"), and changes the element content (innerHTML) to "Hello JavaScript":

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

JavaScript accepts both double and single quotes:

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

In this example JavaScript changes the value of the src (source) attribute of an <img> tag:

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

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

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

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

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

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

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.