Finders Keepers exercise

JavaScript
1

Hello everyone,

I’m doing this exercise where I need to: Create a function that looks through an array (first argument) and returns the first element in the array that passes a truth test (second argument). If no element passes the test, return undefined.
I can do it with for loop but i wanted to do it with some methods.

So I have a 2 questions about my code bellow.

  1. Although my code returns what is first element that pass the test, freeCodeCamp checker doesn’t agree. Why?
  2. I intentionally put “console.log(item)” to see what will be returned when it doesn’t find item. Why i’m not getting “undefined” return ?

Thanks

Your code so far


function findElement(arr, func) {
 let item = arr.filter(func);
 console.log(item)
 if (item ===[]){
   return undefined;
 }
 return item.slice(0,1); 
}
console.log(findElement([1, 2, 3, 4], num => num % 2 === 0));
console.log(findElement([1, 3, 5, 8, 9, 10], function(num) { return num % 2 === 0; }));
console.log(findElement([1, 3, 7, 9], function(num) { return num % 2 === 0; }));
2

generally, [] === [] returns false

This is due to how objects and arrays are compared. You should instead use item.length === 0

The function you’re implementing already exists btw, it’s Array.prototype.find but it’s good to reimplement it in some way I guess

3

You are returning undefined because [] === [] is false. You cannot compare the contents of two arrays using an equality operator. What else can you use to check for an empty array?

4

Thanks for answers guys.

I’ve tried with only .find() method and its cool - in one line code I passed the test. I’m still at beginning and i forgot about this one :slight_smile:

Still, when i write code like this,

function findElement(arr, func) {
 let item = arr.filter(func).slice(0,1); 
 if (item.length === 0){   
   return undefined;
 }
 return item;
}
console.log(findElement([1, 3, 5, 8, 9, 10], function(num) { return num % 2 === 0; }))

code returns 8, but in console I get message:
// running tests
findElement([1, 3, 5, 8, 9, 10], function(num) { return num % 2 === 0; }) should return 8.
// tests completed

…and cant pass the test.

5

Slice returns an array, so you simply need to get the first element of it :slight_smile:

1 Like
6

haha yes, returns array with one element,
and i wanted just the element

thanks