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().

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”;

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JavaScript accepts both double and single quotes:


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

  

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

document.getElementById(“demo”).style.fontSize = “35px”;
or
document.getElementById(‘demo’).style.fontSize = ’35px’;

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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’;

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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’;

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