multi expression ternary operator?

Question

I'm trying to make multiexpression for ternary operator in Javascript like this :

condition ? 
exp1 ; ... ; expN 
:
alternative1 ; ... ; alternativeN

Here my code :

  validateEmail && validatePassword ?
        this.setState({validateForm: true})
        this.setState({nameSubmit:"onSubmit"})
        : null

My console returns me an error :

Declaration or statement expected

The javascript documentation talks about :

Syntax :

condition ? expr1 : expr2

But maybe someone has achieved the multi expression ternary operator ?

Thanks

You want to create a shortcut for "switch()" ? Because the classic boolean condition only knews two possible outcomes. :-) — JanRecker, Jul 18 '18 at 19:12
And what should it evaluate to? `exp1` or `expN` or something inbetween? — Jonas Wilms, Jul 18 '18 at 19:18
@JonasW. He's not trying to do multiple conditions, just multiple expressions in the true and false cases. — Barmar, Jul 18 '18 at 20:08
The real question is *why*? Ternary operators should be used for short conditions and results, they become unreadable if you try to put too much in them. Use `if` for anything complicated. — Barmar, Jul 18 '18 at 20:09
@JanRecker He's not looking for `switch`, he only has one condition, multiple results. — Barmar, Jul 18 '18 at 20:45
@JonasW. Notice also that his example expressions are mainly side-effecting, not value-returning. He just seems to be using the ternary as a replacement for `if`. — Barmar, Jul 18 '18 at 20:47

Aidan Hoolachan · Accepted Answer · 2018-07-18T23:18:44.387

2

const exp = () => { exp1; ... ; expN }
const alt = () => { alternative1; ... ; alternativeN }

condition ? exp() : alt();

It's not very readable you could use an IIFE to create the function and execute it in the same line.

condition ? (() => { exp1; ... ; expN })() : (() => { alternative1; ... ; alternativeN })();

Edit: I think you just added your code. In your code, I would recommend simply merging your setState calls into one command:

this.setState({
  validateForm: true, 
  nameSubmit:"onSubmit"
});

edited Jul 18 '18 at 23:18

answered Jul 18 '18 at 19:19

Aidan Hoolachan

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thanks for the hints, concerning the second form with coma, my console returns me "second argument expect to be a function" – Webwoman Jul 18 '18 at 22:56
Ah, yes I needed to add an arrow function. EdIted answer – Aidan Hoolachan Jul 18 '18 at 23:18
my mistake, I would mean for this.setState({ validateForm: true, nameSubmit:"onSubmit" }); – Webwoman Jul 18 '18 at 23:24
1

I'm positive that that line of code is acceptable, so it must be coming from elsewhere. The full line would be ----- validateEmail && validatePassword ? this.setState({ validateForm: true, nameSubmit:"onSubmit" }) : null ------- Here's a similar question: https://stackoverflow.com/questions/40249934/updating-objects-with-setstate-in-react – Aidan Hoolachan Jul 18 '18 at 23:38

score 1 · Answer 2 · answered Jul 18 '18 at 19:14

1

You can use the comma operator.

The comma operator evaluates each of its operands (from left to right) and returns the value of the last operand.

let a = 0,
    b = 1,
    c = 2,
    d = a === 0 ? (b++, c++) : -1;
    
console.log(b, c, d); // prints 2 3 and 2(because this will be the last expression to be evaluated).

answered Jul 18 '18 at 19:14

Ele

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clever.. hadn't thought of this! – Aidan Hoolachan Jul 18 '18 at 19:42

score 1 · Answer 3 · answered Jul 18 '18 at 19:40

1

To execute multiple statements in one branch there is the if statement:

if(validateEmail && validatePassword) {
   this.setState({validateForm: true});
   this.setState({nameSubmit:"onSubmit"});
}

answered Jul 18 '18 at 19:40

Jonas Wilms

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multi expression ternary operator?

3 Answers3