Number function returning 0

Question

For example, this piece of code:

Number("") + Number("")

I expect to return "" (aka nothing) so I created this function

    function addthese(x, y){
        if (x != ""){
            asdf = Number(x) + Number(y)
            return  Number(asdf)
        } else {
            return ""
        }
    }

But for some reason this function returns NaN
Any help will be appreciated

What input and output are you expecting? Running `addthese("", "")` already returns `""` — thammada.ts, Jun 20 '20 at 06:02
beacuase when don't pass the argument, it will become undefined and Number(undefined) equals to `NaN` — gorak, Jun 20 '20 at 06:02
You are just checking `X` for `""`, what about `Y`, and other values like `undefined` or `abc`? If `Number(Y)` is `NaN` then everything will be `NaN`. — Sandip Nirmal, Jun 20 '20 at 06:19

score 1 · Accepted Answer · answered Jun 20 '20 at 06:03

Perhaps, you might be calling the function without passing in parameters. I did some quick tests and that's the only way i managed to reproduce the "NaN" returning.

If that's the case, the function will "parse" an undefined value, which is not possible and you'll get that ugly NaN you got.

score 0 · Answer 2 · answered Jun 20 '20 at 06:06

0

if you want to cache all cases related to undefined, null, false or "" please use the following code:

function addthese(x, y){
    return isNaN(x) || isNaN(y) ? "" :  Number(x) + Number(y)
}

answered Jun 20 '20 at 06:06

vlad-grigoryan

322
3
11

score 0 · Answer 3 · answered Jun 20 '20 at 06:09

0

Even though the Number function can convert an empty string to 0, for any non-number string, it doesn't have a clue. So, NaN is returned.

console.log(Number(""));
console.log(Number(undefined));
console.log(Number("foo"));

answered Jun 20 '20 at 06:09

Charlie

22,886
11
59
90

Number function returning 0

3 Answers3