Core JavaScript

Callback Functions

This JavaScript example demonstrates how to various types of callback functions, including arrow and anonymous functions.

CallbackFunctions.html

<!DOCTYPE html>
<html>
  <head>
    <title>XoaX.net's Javascript</title>
    <script type="text/javascript" src="CallbackFunctions.js"></script>
  </head>
  <body onload="Initialize()">
  	<div id="idPrime"></div>
  	<div id="idEven"></div>
  	<div id="idLessThan20"></div>
  </body>
</html>

CallbackFunctions.js

function PrintArray(qaArray, sID) {
	document.getElementById(sID).innerHTML = qaArray;
}

function GetArrayOfIntegers(iStart, iEnd, fnTest) {
	let iaArray = [];
	for (let i = iStart; i <= iEnd; ++i) {
		if (fnTest(i)) {
			iaArray.push(i);
		}
	}
	return iaArray;
}

function IsPrime(iN) {
	let iSqrt = Math.floor(Math.sqrt(iN) + .5);
	for (let i = 2; i <= iSqrt; ++i) {
		if (iN % i == 0) {
			return false;
		}
	}
	return true;
}

function Initialize() {
	// Callback with a standard function
	let iaPrimes = GetArrayOfIntegers(2, 50, IsPrime);
	PrintArray(iaPrimes, "idPrime");
	// Callback with a arrow function
	let iaEvens = GetArrayOfIntegers(2, 30, (i) => (i % 2 == 0));
	PrintArray(iaEvens, "idEven");
	// Callback with an anonymous function
	let iaLessThan20 = GetArrayOfIntegers(4, 30, function(i) {return i < 20;});
	PrintArray(iaLessThan20, "idLessThan20");
}
 

Output

 
 

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