javascript ternary if using condition's value as the outcome

Question

In PHP, say if I have code like this:

$aValue = functionThatReturnsAValue(); // the function might return a string or null;
$anotherValue = $aValue ? process($aValue) : null;

only for brievity (IDK is this a good practice or not and also regarding the performance, etc), I used to change the code like so:

$anotherValue = ($aValue = functionThatReturnsAValue()) ? process($aValue) : null;

My questions are:

Is this style even a good practice?
How can I use this with JavaScript? I wrote with same style but got error.

Thank you.

you have assignment in if statement, not a value. if you want to keep this in one line it would be better to write it like this : `$anotherValue = functionThatReturnsAValue() ? process( functionThatReturnsAValue()) : null;` — Maksym Shevchenko, Mar 15 '18 at 08:02
@Xufox i have code like this `aValue: (let a = someFunction()) ? a : null,`. ESLint gave me Unexpected Token. — Rahmat Nazali Salimi, Mar 15 '18 at 08:10
@rahmatNazali That code is completely different from what you posted, and syntactically invalid. — Sebastian Simon, Mar 15 '18 at 08:12
@MaksymShevchenko I definitely may be wrong, but this will run the `functionThatReturnsAValue()` twice, isn't it? Where we could only call it once and save the result on a tmp variable and use it again later. CMIIW — Rahmat Nazali Salimi, Mar 15 '18 at 08:13
@Xufox I just tried to change it like so `let aValue = (let a = Constant.projectName) ? a : null` and I still got the same error. CMIIW — Rahmat Nazali Salimi, Mar 15 '18 at 08:16
well yeah, that's true, it's better to keep value in a variable above, to be honest. By the way, you could check for null in `process()` function, and return null in this case, so you won't need this statement at all. `anotherValue = process(functionThatReturnsAValue());` — Maksym Shevchenko, Mar 15 '18 at 08:17
@rahmatNazali Well… it’s still syntactically invalid. You can’t put a `let` in expression context. — Sebastian Simon, Mar 15 '18 at 08:17
@MaksymShevchenko Thankyou for the kind reply. I have learned a lot from this. — Rahmat Nazali Salimi, Mar 15 '18 at 08:47
@Xufox thankyou for the reply. I tried to change the code to something like this `let a = null; let aValue = (a = Constant.projectName) ? a : null;`. It do works, but it will miss the brievity I am trying to achieve. Anyway thankyou as I also have learned a lot from this. +1 for the duck too! :) — Rahmat Nazali Salimi, Mar 15 '18 at 08:50

Nina Scholz · Accepted Answer · 2018-03-15T08:12:09.507

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You could use a logical AND && and process only a given value.

If aValue is null or a falsy value, this value is assigned to anotherValue, otherwise, it takes the value of process(aValue).

anotherValue = (aValue = functionThatReturnsAValue()) && process(aValue);

edited Mar 15 '18 at 08:12

answered Mar 15 '18 at 08:02

Nina Scholz

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This works for me. Thankyou very much for your suggestion. – Rahmat Nazali Salimi Mar 15 '18 at 08:55

score 0 · Answer 2 · answered Mar 15 '18 at 09:30

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Since aValue is the value returned from executing functionThatReturnsAValue(), You can try this

var anotherValue = (functionThatReturnsAValue()) ? process(functionThatReturnsAValue()) : null;

answered Mar 15 '18 at 09:30

Apetu Gideon

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javascript ternary if using condition's value as the outcome

2 Answers2