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Loops
Nested Loops

When we have a loop running inside another loop, we call that a nested loop. One use for a nested `for` loop is to compare the elements in two arrays. For each round of the outer `for` loop, the inner `for` loop will run completely.

Let’s look at an example of a nested `for` loop:

``````const myArray = [6, 19, 20];
const yourArray = [19, 81, 2];
for (let i = 0; i < myArray.length; i++) {
for (let j = 0; j < yourArray.length; j++) {
if (myArray[i] === yourArray[j]) {
console.log('Both loops have the number: ' + yourArray[j])
}
}
};``````

Let’s think about what’s happening in the nested loop in our example. For each element in the outer loop array, `myArray`, the inner loop will run in its entirety comparing the current element from the outer array, `myArray[i]`, to each element in the inner array, `yourArray[j]`. When it finds a match, it prints a string to the console.

Now it’s your turn to write a nested loop!

### Instructions

1.

Imagine you’re a big-wig programmer for a social media platform! You have been tasked with building a prototype for a mutual followers program. You’ll need two arrays of “friends” from two mock users so that you can extract the names of the followers who exist in both lists. Make a variable called `bobsFollowers` and set it equal to an array with four strings representing the names of Bob’s friends.

2.

Make a variable called `tinasFollowers` and set it equal to an array with three strings representing the names of Tina’s friends. Make exactly two of these the same as two of the friends in the `bobsFollowers` array.

3.

Create a third variable named `mutualFollowers` and set it to an empty array.

4.

Create a nested loop that iterates through `bobsFollowers` as the array for the outer loop and `tinasFollowers` as the array for the inner loop. If the current element from the outer loop is the same as the current element from the inner loop, push that element into the `mutualFollowers` array.