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JavaScript Introduction


JavaScript is the most popular programming language in the world.

This page contains some examples of what JavaScript can do.



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JavaScript Can Change HTML Content


One of many 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";



Try yourself >>


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JavaScript Can Change HTML Attributes


This example changes an HTML image, by changing the src attribute of an tag:

Example


Click the light bulb to turn on/off the light.



Try yourself >>


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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 = "25px";



Try yourself >>


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JavaScript Can Validate Data


JavaScript is often used to validate input:

Example

Please input a number between 1 and 10


Try yourself >>


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