Falsy Bouncer

Learn how to solve the freeCodeCamp algorithm 'Falsy Bouncer' using the Array.filter() method!

Falsy Bouncer

In this freeCodeCamp algorithm we are tasked with removing all falsy values from an array. Oh yeah, and we will get to try our hand at the Array.filter() method!


  • bouncer([7, "ate", "", false, 9]) should return [7, "ate", 9]
  • bouncer(["a", "b", "c"]) should return ["a", "b", "c"]
  • bouncer([false, null, 0, NaN, undefined, ""]) should return []
  • bouncer([1, null, NaN, 2, undefined]) should return [1, 2]

Real-World Use Cases

This is a useful and fairly straight-forward real-world algorithm that you could use in tons of places. The first thought that comes to mind is that it could be used to filter out votes for a proposal in which there's either a yes or a no, a true or false, or a 0 or 1. You could quickly and easily get all the results that are either true or false!


// Create a function that accepts an array
    // Filter the array
        // Return truthy values

Solving the Algorithm

Setting up the function

Let's setup a function that accepts an array.

function bouncer(arr) {

Create the array filter & solve the algorithm

Here we get to take a look at the Array.filter() method which "returns a new array with all elements that pass the test implemented by the provided function".

With that said - we can just return all elements from the array, and the filter itself will return all methods that coerce to true aka "Truthy". A value will coerce to true so long as it is not considered false or "Falsy".

function bouncer(arr) {
  // Don't show a false ID to this bouncer.

	const truthy = arr.filter(item => {
		return item;

  return truthy;
bouncer([7, "ate", "", false, 9])
// bouncer(["a", "b", "c"])
// bouncer([false, null, 0, NaN, undefined, ""])
// bouncer([1, null, NaN, 2, undefined])

Test this code in your browser console


In a fairly straighforward manner, we were able to use the Array.filter() to quickly sort through an array and return all "Truthy" values.

Shoot me an email at [email protected] with any questions and if you enjoyed this, stay tuned and subscribe below! 👇

Help us improve our content