How to iterate over a callback n times in JavaScript?
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.
Here we have some common approaches:
Table of Content
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.
Example: This example uses the above approach.
// 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
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.
Example: This example describes the above explained approach.
// 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
Using Array.from() and Array.prototype.keys() for Index-Based Iteration
In this approach, we'll convert the number of iterations (n) into an array of n elements using Array.from() and then use Array.prototype.keys() to iterate over the indices of the array. This allows us to effectively control the number of iterations and use the index to invoke the callback function.
Example: This example demonstrates the usage of Array.from() and Array.prototype.keys() to iterate over a callback function multiple 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 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
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.
Syntax
Array.from({ length: n }).forEach((_, index) => callback(index + 1));Example: The example below demonstrates how to use the forEach() method to iterate over 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
