How to iterate over a callback n times in JavaScript ?

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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: We use 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.

Javascript

<script> 
    // 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); 
</script>

Output:

01 02 03 04
01 02 03
01 02
01

Approach 2: We use 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.

Javascript

<script> 
    // 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); 
</script>

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

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