Remove all falsy values from an array

You can use Boolean :

var myFilterArray = myArray.filter(Boolean);

Since you want to get rid of "falsy" values, just let JavaScript do its thing:

function bouncer(arr) {
  return arr.filter(function(v) { return !!v; });
}

The double-application of the ! operator will make the filter callback return true when the value is "truthy" and false when it's "falsy".

(Your code is calling isNaN() but not passing it a value; that's why that test didn't work for you. The isNaN() function returns true if its parameter, when coerced to a number, is NaN, and false otherwise.)

edit — note that

function bouncer(arr) {
  return arr.filter(Boolean);
}

would work too as LoremIpsum notes in another answer, because the built-in Boolean constructor does pretty much the exact same thing as !!.

truthyArray = arr.filter(el => el)

^ that's how you do it