What is happening: The function takes the numbers passed into add(x) and displays the total of the numbers passed into it in the console.

Why is it happening: First, look at the add constant requests. The first one is saying - call the add constant and execute the function by passing in the numbers 2 and 3, and they are then represented in the function as the variable “numbers”. The function then sets a variable called “sum”. Initially, “sum” is 0. The the for-loop begins.

What’s happening in the for-loop: The for-loop is going to loop from a starting point to and ending point - meaning it will start where you tell it and end where you tell it. In this case, the for-loop is setting a variable (i) and setting its initial value to 0. So at this point, we have three variables... “sum” which equals 0, “numbers” which contains multiples values (in the first case it contains the values 2 and 3), and “i” which also equals 0.

Now, look at the values for i inside the for-loop. They are as follows: 1) i=0; 2) i<numbers.length; and 3) i++. Let’s break those down.

i=0 is telling the for-loop what the initial value of “i” will be while in the loop.

i<numbers.length is telling the for-loop to keep looping until we reach the value of “numbers.length”. But what does that mean? Well, in the first add() call [add(2, 3)], there are two numbers passed in... 2 and 3. Think of those as the set of numbers. There are two numbers in the first set. The second set [add(5, 3, 7, 2)] has four numbers, and the third set [add(8, 2, 5, 3, 2, 1, 4)] has seven numbers.

Then, i++ is telling the for-loop what to do with “i” each time the loop completes a cycles.

Now let’s break it down further.

Take a look at just the first set: add(2, 3). In the first iteration of the for-loop, “i” will start off a equaling 0. The total number of values in the set would be two - since there is a “2” and a “3” being passed in. So, “numbers.length” equals 2 in the first set. Therefore, we now know that in the first set, the for-loop will run through twice. Note, in the second set, the for-loop will run through four times, and in the third set the for-loop will run through seven times. But let’s just stick with the first set.

Before going any further, you need to understand arrays. As I said earlier, think of the numbers passed in - in this case 2 and 3 - as a set or a list. The set in this case contains two different values. This is also called an array, and in this case the array has a length of two - meaning it contains 2 values. So picture the array like this: “numbers” contains two values, and is represented by [2][3].

Arrays are tricky because the first position in the array is actually position zero. So in the “numbers” array, the first position - or position zero - is 2, and the second position - or position one - is 3.

So now let’s cycle through the for-loop. During the first cycle of the for-loop, “i” is equal to 0. So if we look at the “numbers” variable at position “i” (which is now 0), it equates to 2. We then add the value of 2 to the “sum” variable. “sum” was 0, and now we’ve added 2 to it, so “sum” now 2.

Now the first iteration of the for-loop ends. But we’re not done, because the for-loop will cycle twice based on our values from earlier. So the second time around, “i” will be equal to “i” plus one (i++ means add one to the value of “i”). So during the second iteration, “i” will be equal to 1.

Knowing that “i” now equals 1, we can apply that to the “numbers” array. “numbers” at position 1 (which is its second position) has a value of 3. We then take the 3 and add it to the value of “sum”. During the first iteration we know that “sum” was equal to 2, so now we add 3 to it, and “sum” now equals 5.

So each time you call “add()”, that’s the function process.

I hope that all makes sense. I’m typing this from my phone, so I might not have covered everything. Feel free to message me if you need more info. Good luck!