JS Introduction

JavaScript Introduction

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This page contains some examples of what JavaScript can do.

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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 accepts both double and single quotes:

Try it

Example

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

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JavaScript Can Change HTML Attributes

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

The Light Bulb

Try it

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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

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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

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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

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