calculateTimeTaken()

Step 1: Defining the Problem

We are given a task to calculate the time taken by some process in JavaScript. Basically, we can use the JavaScript Date object to get the start time and end time and by subtracting them we can get the time taken by the process.

Step 2: Starting the Function

The first step is to define our function. The function doesn't take any arguments as we'll be capturing the start and end times within the function itself. For now, our function does nothing.

function calculateTimeTaken() {
}

Step 3: Capturing the Start Time

In the function calculateTimeTaken we'll first capture the start time before any process starts. Here's how we can do that:

function calculateTimeTaken() {
   let startTime = new Date();
}

The new Date() command gets the current time.

Step 4: Completing the Operation

In real-life scenario, between capturing the start time and end time we will perform some operations (like calculation, data fetch/payment processing, etc) – Equating it to a delay here for understanding:

function calculateTimeTaken() {
   let startTime = new Date();

   // simulate a delay using setTimeout function
   setTimeout(() => {
     // operations go here
   }, 2000);
}

Step 5: Capturing the End Time and Calculating the Difference

Within the setTimeout function we are simulating the time taken by our hypothetical operations. Once these operations are complete, we'll capture the time again and subtract the start time from this. This will give us the time taken by the operations.

function calculateTimeTaken() {
   let startTime = new Date();

   setTimeout(() => {
     // end time
     let endTime = new Date();
     
     // time difference in ms
     let timeDiff = endTime - startTime;
     
     // strip the ms
     timeDiff /= 1000;
     
     // get seconds 
     let seconds = Math.round(timeDiff);
     console.log(seconds + " seconds.");
     
   }, 2000);

}

Conclusion

This is the simplest way to measure execution time in JavaScript. Note that JavaScript is a single-threaded, non-blocking concurrent language, which means operations don't necessarily complete in the order they're initiated. In a real-world application, you'd typically use promises or callbacks to ensure operations complete before you stop the timer.

So, in this function calculateTimeTaken(), we managed to calculate the time taken by some process using JavaScript's built-in Date object and math operations.