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# How to iterate over a callback n times in JavaScript ?

• Last Updated : 30 Dec, 2022

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

 ``

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

 ``

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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