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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":

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 »


JavaScript Can Change HTML Attribute Values
In this example JavaScript changes the value of the src (source) attribute of an <img> tag:

The Light Bulb

Turn on the light

Turn off the light


Try it Yourself »









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";
Try it Yourself »


JavaScript Can Hide HTML Elements
Hiding HTML elements can be done by changing the display style:

Example

document.getElementById("demo").style.display = "none";
Try it Yourself »


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";
Try it Yourself »


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.

JavaScript Versions »













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Reference: https://www.w3schools.com/js/js_intro.asp