Can the JS array length property ever return a negative value?

Question

Would there ever be an instance when the JavaScript array length property returns a negative value? I'm assuming the answer is no, but I was wondering if there would ever be a need to account for negative values when comparing the length of an array in an if statement, for example.

var x = y.length;

if (x === 0) {
    return false;
  } else if (x > 0) {
    return true;
  } else alert("error"); // is this necessary?
}

Answer 1

No.

The spec for the length property says:

The length property of this Array object is a data property whose value is always numerically greater than the name of every deletable property whose name is an array index.

There cannot be -1 properties.

Also, and more explicitly, the spec for Array says:

Every Array object has a length property whose value is always a nonnegative integer less than 2³².

Update: Answer still holds for ES2020

Answer 2

Not normally (as other answers have pointed out), but an object that is an instance of an array can have a negative property called length

var b = Object.create([]);
b.length = -1;

alert(b instanceof Array)
alert(b.length);