Basic Algorithm: False bouncer

JavaScript
1

Hello fellow learners!

I was working on the False bouncer test, and finally found the solution: so this question is not about finding the solution.

However, while working on it, I tried a couple of things and I came upon two similar codes which give two different outcomes: I just don’t get why it’s different. Can anybody explain why, please?

function bouncer(arr) {
  var filtered = arr.filter(function (value){
      return value !== undefined;
  })
  console.log(filtered);
}

bouncer([false, null, 0, NaN, undefined, ""]);

returns [false, null, 0, NaN, ""]

function bouncer(arr) {
  var filtered = arr.filter(function (value){
    if(value !== undefined){
      return value;
    }
  })
  console.log(filtered);
}

bouncer([false, null, 0, NaN, undefined, ""]);

returns []

ThanX !

2

Your second filter function always returns a falsy value (see code comments for why):

function bouncer(arr) {
  var filtered = arr.filter(function (value){
    if(value !== undefined){
      return value; // all the `value`s in the array are falsy
    }
    // else return `undefined` (in JavaScript, `undefined` is the default return
    // value when no `return` statement is run). `undefined` is also falsy.
  })
  console.log(filtered);
}

bouncer([false, null, 0, NaN, undefined, ""]);

Because all the return values are falsy, everything is filtered out.

1 Like
3

Of course !!! “if” works as a truth checker!

if (something true){
return whatever you say
}

Whereas in the first one, I was returning what was undefined!
(⁄ ⁄•⁄ω⁄•⁄ ⁄) What an idiot I am!

Thanks for taking the time to answer, @lionel-rowe ! Much appreciated.

4

No problem! :slight_smile:

Don’t put yourself down, even the best programmers need an extra pair of eyes on their code from time to time. :wink:

1 Like