JavaScript Variable Change Value

In this tutorial we will learn How To Change Variable Value in JavaScript. We can use JavaScript function to change the variable value by reassigning it a new value. We can also do this outside of function.

HTML Code

HTML Code is given below, in this code we have a paragraph tag to display the new value of the variable.

<!DOCTYPE html>
<html>
<head>
<title>JavaScript Variable Change Value</title>
</head>    
<body> 
    
<p id="output"></p>    
    
<script src="script.js"></script>    
</body>
</html>

JavaScript Code

Take a look at the JavaScript code, in this code we have a variable with value = 100. This value is then changed to 200 inside a user defined function.

Function is then called to change the value. Value will not change without the function call because a JavaScript function is only executed on function call.

getElementById() method is used to select the paragraph tag and innerHTML property is used to display the changed value of variable.

<script>
var variable = 100;

function changeValue()
{
  variable = 200;
}
changeValue();
document.getElementById('output').innerHTML = variable;
</script>

Variable declared outside function is global variable.

Variable declared inside function is local variable.

We can also do this without function.

<script>
var variable = 100;
variable = 200; //simple reassignment
document.getElementById('output').innerHTML = variable;
</script>

Demo

Video Tutorial

Watch video tutorial on How To Change Variable Value with JavaScript.

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