How to iterate over a callback n times in JavaScript?
Last Updated :
15 Oct, 2025
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Given a callback function, we have to iterate over a callback n times. The callback is a function that is passed as an argument. To iterate over the callback function, we have to run the callback function n time.
[Approach 1]: Using recursion to iterate the n times callback function
- First, create a callback function factor that takes n as an argument.
- The factor function generates a pattern of n length.
- Create a test function that takes a callback function and n.
- The test function checks the value of n is equal to 0 and not.
- If n is 0 it returns the terminate test function, else it calls the callback function which prints the pattern.
// callback function that print pattern
function factor(n) {
// base case for recursion
if (n <= 1) {
console.log("0" + n);
return;
}
// string to store patterns
let str = "";
// loop for generate pattern
for (let i = 1; i <= n; i++) {
str += `0${i} `;
}
// printing patterns
console.log(str);
// recursion call with decrement by 1
return factor(n - 1);
}
// function to run callback function
function test(n, callback) {
if (n == 0) {
console.log("please provide value n greater than 0");
return;
}
let k = n;
//calling callback function
callback(k);
}
// initialising test number
let t_number = 4;
// calling main function to call callback function
test(t_number, factor);
Output
01 02 03 04 01 02 03 01 02 01
[Approach 2]: Using a loop statement to iterate over the callback.
- First, we create a callback function factor which generates a factorial of numbers.
- Create a test function with argument n and a callback function.
- Check the value of n if it is invalid terminate if not continue.
- Create for loop with range n.
- On each loop call the callback function which prints the factorial of each number.
// call back function that return factorial
function factor(number) {
let j = 1;
// loop that generate factorial of number
for (let i = 1; i <= number; i++) {
j *= i;
}
// printing value of factorial
console.log(`factorial of ${number} is `);
console.log(j);
}
// function that iterate over callback function
function test(n, callback) {
if (n <= 0) {
console.log("invalid number");
return;
}
let k = n;
// iterating over callback function with for loop
for (let i = k; i >= 1; i--) callback(i);
}
// initialising test variable
let t_umber = 5;
// main function calling
test(t_umber, factor);
Output
factorial of 5 is 120 factorial of 4 is 24 factorial of 3 is 6 factorial of 2 is 2 factorial of 1 is 1
[Approach 3]: Using Array.from() and Array.prototype.keys() for Index-Based Iteration
- Convert the number of iterations (
n) into an array ofnelements usingArray.from(). - Use
Array.prototype.keys()to get an iterator over the array indices. - Iterate over the indices to control the number of iterations.
- Use the index in each iteration to invoke the callback function effectively.
// Callback function that prints the index
function printIndex(index) {
console.log(`Iteration ${index}`);
}
// Function to iterate over callback function
function iterateCallback(n, callback) {
if (n <= 0) {
console.log("Invalid number of iterations");
return;
}
// Create an array of size n, then iterate over its keys
Array.from({ length: n }, (_, index) => callback(index + 1));
}
let numIterations = 5;
iterateCallback(numIterations, printIndex);
Output
Iteration 1 Iteration 2 Iteration 3 Iteration 4 Iteration 5
[Approach 4]: Using forEach() Method
The forEach() method can be used to iterate over an array. By creating an array of a specified length using Array.from(), we can use forEach() to call the callback function n times.
// Callback function that prints the index
function printIndex(index) {
console.log(`Iteration ${index}`);
}
// Function to iterate over callback function
function iterateCallback(n, callback) {
if (n <= 0) {
console.log("Invalid number of iterations");
return;
}
// Create an array of size n, then iterate over its elements
Array.from({ length: n }).forEach((_, index) => callback(index + 1));
}
let numIterations = 5;
iterateCallback(numIterations, printIndex);
Output
Iteration 1 Iteration 2 Iteration 3 Iteration 4 Iteration 5
Syntax:
Array.from({ length: n }).forEach((_, index) => callback(index + 1));
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