Javascript: Determine if argument is passed to function

Question

WAIT! Before you down-vote and/or mark this as a duplicate, please read:

I've reviewed quite a few answers on SO regarding determining if an argument (parameter, variable, etc.) is passed to a function, including this and this.

However, the consensus answer is to check for undefined, one way or another. But that's not necessarily accurate. What if an argument is passed that is itself undefined?

Basically I'm looking to differentiate between:

var a = [1,2][2]  // where this will result in undefined
myFunction(a);

vs.

myFunction();  // where no variable whatsoever is passsed.

The answer could simply be that this is impossible and the undefined variable should be caught before being sent the function, but was hoping there was another way.

Here's a JSFiddle where I tried to see if any of the previous suggestions were different between the two above scenarios - with no luck.

If this is truly a duplicate question, please point me in the right direction.

score 1 · Answer 1 · answered Feb 27 '19 at 22:33

1

What you can do is iterate through arguments with some and check if any values passed are falsy (undefined, null, NaN, 0, "" or false):

function myFunction() {
    if (arguments.some(e => !e)) {
        console.log("Falsy value passed");
    } else {
        //Rest of function goes here
    }
}

answered Feb 27 '19 at 22:33

Jack Bashford

43,180
11
50
79

Thanks Jack - I wasn't aware of the `arguments` object, that seems to be the crux of the problem. – elPastor Feb 27 '19 at 22:40
No problem @elPastor, if my answer fixed your problem, please mark it as accepted. – Jack Bashford Feb 27 '19 at 22:40
trincot's comment was what did it, but I appreciate your help. – elPastor Feb 27 '19 at 22:42

Javascript: Determine if argument is passed to function

1 Answers1