How to pass undefined into a function param

Question

What is the proper way to send undefined as the value here in my test:

 it('returns response with no content status for no data found', function (done) {
        gateway.data('undefined');
        ...rest of code
        done();
    });

or should I do gateway.data(undefined); or gateway.data("undefined");

purpose is I'm setting it to defined on purpose because my test needs to test that case in the calling function.

here's the gateway.data function:

module.exports = {
    data: function(someData){
        globalData = someData;
    },
    findAll: function(){
        return globalData;
    }
};

If you don't pass a value, the parameters are set to `undefined` implicitly. However, if you are working with `arguments`, then there is a big difference between `foo(undefined)` and `foo()`. — Felix Kling, Jul 24 '15 at 19:12
possible duplicate of [How to pass the value 'undefined' to a function with multiple parameters?](http://stackoverflow.com/questions/8998612/how-to-pass-the-value-undefined-to-a-function-with-multiple-parameters) — SK., Jul 24 '15 at 19:26

score 2 · Answer 1 · answered Jul 24 '15 at 19:08

2

You should go with gateway.data(undefined); as the others are passing a string and not undefined.

answered Jul 24 '15 at 19:08

Rob M.

35,491
6
51
50

score 2 · Answer 2 · answered Jul 24 '15 at 19:11

2

The best way is to call gateway.data(); someData will be undefined in this case

answered Jul 24 '15 at 19:11

Hayk Mantashyan

328
2
18

manoj · Answer 3 · 2015-07-24T19:13:23.067

0

 gateway.data(undefined);

as undefined is not a string but a variable

edited Jul 24 '15 at 19:13

answered Jul 24 '15 at 19:09

manoj

3,391
2
20
30

1

Actually, `undefined` is *variable*. It is not a [keyword](http://www.ecma-international.org/ecma-262/6.0/index.html#sec-keywords). – Felix Kling Jul 24 '15 at 19:11
Thank you .. I now under stand that – manoj Jul 24 '15 at 19:13

score 0 · Answer 4 · answered Jul 24 '15 at 19:10

0

Pick one:

gateway.data(undefined);
gateway.data(void 0);
gateway.data();

answered Jul 24 '15 at 19:10

Sebastian Nette

7,364
2
17
17

score 0 · Answer 5 · answered Jul 24 '15 at 19:13

0

gateway.data(); // implicitly: someData becomes undefined

About function arguments.

answered Jul 24 '15 at 19:13

Vidul

10,128
2
18
20

score 0 · Answer 6 · answered Jul 24 '15 at 19:23

0

gateway.data(undefined); this way should work, what is the problem?

Also, the void operator seems to be the most common way to explicitly get undefined.

See here

answered Jul 24 '15 at 19:23

SK.

4,174
4
30
48

How to pass undefined into a function param

6 Answers6