Kevin Powell - Community•14mo ago

Javascript nested loops for beginners

Hello folks! Why does this code print 1 2, and not the names that are similar in the arrays? Comes from codecademy's JS beginner course

const bobsFollowers = ['Tim', 'Kim', 'Lim', 'Nim'];
const tinasFollowers = ['Kim', 'Nim', 'Hue'];
const mutualFollowers = [];

for (let i = 0; i < bobsFollowers.length; i++) {
    for (let j = 0; j < tinasFollowers.length; j++) {
        if (bobsFollowers[i] === tinasFollowers[j]) {
            console.log(mutualFollowers.push(bobsFollowers[i]));
        }
    }
}

const bobsFollowers = ['Tim', 'Kim', 'Lim', 'Nim'];
const tinasFollowers = ['Kim', 'Nim', 'Hue'];
const mutualFollowers = [];

for (let i = 0; i < bobsFollowers.length; i++) {
    for (let j = 0; j < tinasFollowers.length; j++) {
        if (bobsFollowers[i] === tinasFollowers[j]) {
            console.log(mutualFollowers.push(bobsFollowers[i]));
        }
    }
}

8 Replies

Jochem•14mo ago

take a look at the function definition on MDN: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/push It says under Return value:

The new length property of the object upon which the method was called.

if you want to log out the follower's name, either outside the loops run console.log(mutualFollowers); or inside the loop where you have it now log out bobsFollowers[i]

Chris Bolson•14mo ago

both push() and unshift() return the length of the array, not the contents

Å Marlon G•14mo ago

Ok, then that makes sense, but why 1 and 2? Is that the indeces of the bobs when tinas match?

Jochem•14mo ago

it's the length of mutualFollowers after the push operation when it runs into Kim, it pushes Kim to the mutualfollowers array and returns 1 for the new length then it runs into Nim, and pushes that to mutualFollowers, and logs out 2 for the number of items in mutualFollowers after pushing Kim and Nim

Å Marlon G•14mo ago

Ah! Now I see, so i mixed up index number of each content, and the content number it self. I was expecting the index number of bobs to appear.

Jochem•14mo ago

that's simply not what push returns

Å Marlon G•14mo ago

Got it! Thanks! 👏

Jochem•14mo ago

np!

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Javascript nested loops for beginners