!arr would be wrong too. Array is an Object and any object is true-ish.

Because in JavaScript [] == [] returns false - you cannot directly compare arrays. I suggesting reading this or this for information why. If you are checking an empty array, I suggest using Boolean, e.g. if !arr or arr.length==0.

Edit: Fuck, jinx beat me to it again :P

Wrong: arr==[]
Right: arr.length==0

My code:

function isIntArray(arr) {
if(arr == []) {
return true;
}
}

is returning "undefined" on the first test - how??