Difference between return and return false

Question

Let's say in a javascript function I have:

function myfunction (x) {
    if (x===0) {
         return false; //return;
    };
    //some code
};

Is there a difference between return or return false?

I'm asking because someone advised me to use just return (and he do not explained why).

I'm using it for exit the function without doing nothing more. In this simple example I could use if (x!==0) {}; but in longer function maybe (tell me if I'm wrong) is not a good idea to have nested if statement.

`return` returns `undefined` (or `void 0`) (void), while `return false` returns exactly `false` (boolean). Both are **falsy** (https://developer.mozilla.org/it/docs/Glossary/Falsy) values, but they actually are different. In your case, anyway, there is no difference whatsoever, it largely depends on the usage of the function, which will still likely work as intended in most of the cases (if not all the cases) — briosheje, Dec 01 '17 at 16:53
If you just want to exit the function, it doesn't matter at all. — , Dec 01 '17 at 16:54

score 8 · Accepted Answer · answered Dec 01 '17 at 16:59

Just consider this code

function myFunc(){
  return; // exists function and returns `undefined`
}
const myVar = myFunc() // myVar === undefined

and with false

function myFunc(){
  return false; // exists function and returns `false`
}
const myVar = myFunc() // myVar === false

in both caes you this will be same:

if (!myFunc()) { console.log('this gets executed if falsy value is passed') }

So they are almost the same for this use case (note that if you make any other kind of comparison with === it is different story), and which one should you prefer to use?

I would recommend always return something, in this case false because if your function doesn't have return statement then it will always return undefined. So for sake of easier debugging, it's better to return false rather than undefined, because you will imminently know that return statement was indeed executed, while with undefined you have 1 more step to check.

entio · Answer 2 · 2017-12-01T17:00:27.963

return false returns false

return returns undefined (which is falsey)

For most use cases it does not really matter, however if you check their types:

typeof undefined   //returns "undefined"
typeof false       //returns "boolean"

it's just different type.

Moreover:

undefined === false   //identity check returns false
undefined == false    //equality returns true

I can't find a reason to prefer one over another.

score 1 · Answer 3 · answered Dec 01 '17 at 16:56

1

considering

var value = myfunction(0)

value would equal false if you used return false. otherwise it would remain "undefined' if you used an "empty" return

answered Dec 01 '17 at 16:56

Chad

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Difference between return and return false

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