FAQ: Code Challenges: Intermediate JavaScript - findMyKeys()


This community-built FAQ covers the “findMyKeys()” exercise from the lesson “Code Challenges: Intermediate JavaScript”.

Paths and Courses
This exercise can be found in the following Codecademy content:

Web Development

FAQs on the exercise findMyKeys()

Join the Discussion. Help a fellow learner on their journey.

Ask or answer a question about this exercise by clicking reply (reply) below!

Agree with a comment or answer? Like (like) to up-vote the contribution!

Need broader help or resources? Head here.

Looking for motivation to keep learning? Join our wider discussions.

Learn more about how to use this guide.

Found a bug? Report it!

Have a question about your account or billing? Reach out to our customer support team!

None of the above? Find out where to ask other questions here!


Hi I’m a bit stuck on this code challenge. I’m not sure why my function declaration isn’t correct - it outputs undefined:

const findMyKeys = arr => arr.findIndex(item => item === ‘keys’) //This is the correct one resulting in 4

const findMyKeys =(arr)=>{
arr.findIndex(item => item === ‘keys’)}; //This was my answer(only difference is adding () around the parameter and {} brackets

//The rest of the code is here for context: //
const randomStuff = [‘credit card’, ‘screwdriver’, ‘receipt’, ‘gum’, ‘keys’, ‘used gum’, ‘plastic spoon’];


The question was to create a function that finds the index of ‘keys’ in randomStuff. Is there a certain rule of how functions can be notated that I’m missing, I thought it was acceptable to put () around parameters and {} brackets for multi-line returns.
I recognize its shorter syntax as its only a single parameter and a single line return but does that mean you’re only allowed to use the shortened syntax?

Any help would be really appreciated


When a block is used to wrap the function, it must contain a return. A single parameter may be written with or without parens. No parameter or multiple parameters must be in parentheses.

foo = bar => func(bar)

foo = (bar) => func(bar)

foo = bar => {
    return func(bar);

foo = (bar, func) => func(bar)

foo = (bar, func) => {
    return func(bar);


Ah ok, that makes sense now. Many thanks!

I also struggled with interpreting some of the MDN definitions for iteration methods. A few of them have square brackets when describing the callback function usage:

arr.findIndex (callback(element[, index[, array]])[, thisArg])
arr.every(callback[, thisArg])

I made do with some examples, but what are the square brackets meant to signify in this case?


They are meant to signify optional arguments. The one out front that is not in brackets is a required argument.

arr.findIndex (callback(element))