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Viren B
Viren B

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Solving "Finders Keepers" / freeCodeCamp Algorithm Challenges

Post can also be found on my website

Finders Keepers Challenge on fCC

Let's solve freeCodeCamp's Basic Algorithm Scripting Challenge, "Finders Keepers"

Our Starter Code (& Tests)

function findElement(arr, func) {
  let num = 0;
  return num;

findElement([1, 2, 3, 4], num => num % 2 === 0);

// Tests
findElement([1, 3, 5, 8, 9, 10], function(num) { return num % 2 === 0; }) should return 8.
findElement([1, 3, 5, 9], function(num) { return num % 2 === 0; }) should return undefined.

Our Instructions

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.


  • We have two arguments as inputs, one being a arr being an array, func being a function
  • We have to return a number or undefined, based on tests
  • Will have to compare the array in arr against the constraints in func

Further Thoughts

Reading the instructions again, we will have to check the array against the function provided in func, returning the first num which meets the constraint. If there are no values in the array which pass the 'test' in func, return undefined.

So reading this, I figure we should be using some sort of loop on the arr, checking each value against the func test.

I usually will try to use a more modern method, like map(), but I don't think it is the best case since we kind of have to 'break' out of the loop once we meet the first value which is true against the func test.

The starter code gives us let num = 0. I will change that to let num; so it is undefined to start with. If no values within the array pass the test, we will still return num, giving us undefined.

I will opt for a for loop, looping through the array, and will set num to the value of the array's index which is true, then immediately return num;

I want to immediately return the first value because of one of the tests. Looking at the below,

findElement([1, 3, 5, 8, 9, 10], function(num) { return num % 2 === 0; }) should return 8.

Both 8 and 10 are divisble by 0, so if we do not break out of the loop, num would eventually be set to 10, overwriting 8. We want 8 though.

Here is a little pseudo pseudocode:

function findElement(arr, func) {
  create num variable, assign no value yet  
  for (let i = 0; i < arr's size; i++) {
    if (func(arr[i]) is true) 
        set num equal to arr[i]
        return num to stop the loop    

  return num



function findElement(arr, func) {
    let num;
    for (let i = 0; i &lt; arr.length; i++) {
        if (func(arr[i])) {
            num = arr[i];
            return num;
    return num;

Links & Resources

Repeat a String Repeat a String Challenge on fCC


Donate to FCC!

Solution on my GitHub

Thank you for reading!

Top comments (1)

myblood profile image
Alexandr Vasilyev

Thank you for your article. But what is the purpose of &lt in the loop code?