FAQ: Code Challenges: Intermediate JavaScript - findMyKeys()

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

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FAQs on the exercise findMyKeys()

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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’];

console.log(findMyKeys(randomStuff))

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);
}
1 Like

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))

arr.every(callback)
1 Like

I can’t understand my error in this code :
function findMyKeys(array) {
for (let i = 0; i < array.length; i++) {
if (array[i] === ‘keys’) {
return i;
} else {
return -1;
}
}
}

Are you getting an error in the console, or an SCT error message?

In your code, you are only able to check the first item in the array. If the first item is equal to ‘keys’ you return its index, but if it isn’t, you return -1. Since both conditions include a return statement, your function is terminated after the first element is tested. You need to refactor your code, so that you can iterate through the array until you find your ‘keys’. Might consider using the built in methods .indexOf() or findIndex(). Your way will work with a little tweaking, but the built in methods are worth consideration.


Good luck && happy coding!

The code editor is showing this error - “Your function should return the index in the array where ‘keys’ are located.”

1 Like

Why is the function terminated because of two return statements in different conditions ? Also, the if else statement is nested inside a for loop which iterates through the array.

Whenever we depend upon a loop to fully complete iteration of an object, we must not have a return in both clauses of an if statement.

Above, when keys is found, we can return its index; but, not anything else. Let the loop terminate on its own terms (after complete iteration) and if it reaches the end, then after the loop, return -1.

1 Like

Ditto @mtf. After your first if condition is evaluated, one of the two code blocks will execute: the if block if the condition is true; the else block if the condition is false. Since both blocks have a return, the execution of the function is terminated. return ALWAYS sends control back to the line of code that called the function or method. As @mtf stated, you need to return the index of ‘keys’ if you find them, or return -1 after your loop has fully iterated over the entire array. Give it another try, and reply again if you’re still stuck. Your basic structure should resemble this:

function findMyKeys(array) {
  for(let i = 0; i < array.length; i++) {
    //if statement to determine if you've found 'keys'
      //return i
  }
  //if your code reaches this point, you haven't found 'keys'
  //even after searching the entire array,
  //so you can return -1
  //no need for an else statement at all
}

Good luck && happy coding!!

1 Like

Thanks. The code worked.

1 Like

Thanks for helping. The code worked.