Falsy Bouncer Challenge

1

Hello all,

I’m trying to better understand how filter() works in JS.
Here my attempt at pulling only true values from an array:

function bouncer(arr) {
  // Don't show a false ID to this bouncer.
  arr.filter(function(val){
  return val !== false || null || "" || undefined || NaN; 
  }); 
  
  return arr;
}

bouncer([7, "ate", "", false, 9]);

Any guidance is appreciated.

3

Also, double check the documentation on filter function and see what filter returns.
Hint: Does filter mutate the array or return an array?

4

Thanks Reggie01 and rmdawson71.

Still a bit lost, but I’ll keep reading the documentation and try again tomorrow.

function bouncer(arr) {
  // Don't show a false ID to this bouncer.
  arr.filter(function(val){
    
    if(val === false){
      return true;
    }
    else if(val === null){
      return true;
    }
    else if(val === 0){
      return true;
    }
    else if(val === undefined){
      return true;
    }
    else if(isNaN(val)){
      return true;
    }
    else if(""){
      return true;
    }
    else{
      return false;
    }
     
  }); 
  
  return arr;
}

bouncer([7, "ate", "", false, 9]);
6

Firstly, Array.prototype.filter() returns a new array. It does not mutate the working copy. A simple return arr.filter(...) should be enough.

Secondly, read up this definition on Truthy values, that should point out how to check for the values you need.

7

Welp. I’m losing my damn mind over this one. Even though the comparisons for array items '' and false evaluate as false, return arr.filter still returns the whole array, despite @wesleywerner advice. Any thoughts? thanks!

function bouncer (arr) {
  return arr.filter(function (item) {
   return item !== false || item !== null || item !== 0 || item !== '' || item !== undefined || item !== isNaN
  })
}

bouncer([7, 'ate', '', false, 9])
9

thanks @rmdawson71 ! don’t know how I missed that…