JavaScript callback function | Simple example code

A JavaScript callback function is a function passed into another function as a parameter.

Using a callback, you could call another function with a callback, and let the first function run the callback after all statements completed.

JavaScript callback function Example

In the HTML example, addNum function accept 3 parameter. Where is 3rd parameter is callback function – displayResult.

So what is happening:-

First addNum will finish the addition of 2 number, then it will call the displayResult function to show the result.

<html>
<body>

	<p>Addition of numebr is: </p>

	<p id="demo"></p>

	<script>
		function displayResult(some) {
			document.getElementById("demo").innerHTML = some;
		}

		function addNum(num1, num2, myCallback) {
			let sum = num1 + num2;

			myCallback(sum);
		}

		// Test case
		addNum(10, 5, displayResult);


	</script>
</body>
</html>

Output:

JavaScript callback function example code

Q: When to Use a JavaScript Callback function?

Answer: The benefit of using a JS callback function is that you can wait for the result of a previous function call and then execute another function call.

Do comment if you have any doubts and suggestion on this JS function topic.

Note: The All JS Examples codes are tested on the Firefox browser and the Chrome browser.

OS: Windows 10

Code: HTML 5 Version


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