Find out how many times a function has been invoked. | Frontend Interview Question

Question:

We've the following function greet, we need to find out how many times this function has been called.

function greet(){
  console.log("Hello World!");
}

Approach-1

Using a global variable to maintain a count of the number of times this function can be called.

let count = 0;
function greet(){
  count++;
  console.log("Hello World");
}
greet();
greet();
greet();
console.log(count); // 3

Problem: This approach works fine, but there's an issue that, any other part in the codebase can manipulate the count variable.

Approach-2

Using Function Closure

function getGreetings(){
  let _count = 0;
  function greet(){
    _count++;
    console.log("Hello, my name is Shivaansh");
  }
  function getGreetCount(){
    console.log(_count);
  }
  return {
    greet,
    getGreetCount
  }
}

let {greet, getGreetCount} = getGreetings();
getGreetCount();
greet();
greet();
greet();
getGreetCount();
greet();
greet();
getGreetCount();

O/P

Approach-3

Using IIFE

const {greet, getCount} = (function(){
  let count = 0;
  function getCount(){
    return getCount;
  }
  function greet(){
    count++;
    console.log("Hello World");
  }
  return {
    greet,
    getCount
  };
})();
greet();
greet();
greet();
console.log(getCount); // 3

With this approach, we can ensure that no other piece of code can change the count variable. Here the greet function will have a closure with the count variable so with the use of concepts like IIFE and Closures, we would be able to achieve the requirement.

Approach-4

Using Classes

class Greet {
  #msg = "Hello World";
  #count = 0;
  printMessage() {
    this.#count += 1;
    console.log("Hello World");
  }
  getCount() {
    console.log(this.#count);
  }
}
const greet = new Greet();
greet.printMessage();
greet.printMessage();
greet.printMessage();
greet.getCount();
greet.printMessage();
greet.getCount();

O/P.

Here we've created a class User and 2 private properties (Private Properties in a class in Javascript are those with a # prefix attached to them).
In this way, we encapsulate the count from the outer scope and hence achieve our target of tracking the function called time.