CODEWITHSUNDEEP
javascript
Gergő Horváth
Gergő Horváth

Reputation: 3705

Return multiple values in ternary operation

I cannot expain more than an example:

let a = 0;
let b = 2;
let condition;
condition ? a = 2; b = 10 : false
console.log(a, b)

Why this syntax is wrong?

Upvotes: 3

Views: 7608

Answers (6)

Uddeshya Singh
Uddeshya Singh

Reputation: 59

I am relatively new to javascript and I am not really sure about my answer here, but aren't ternary operators somewhat used like this:

condition ? a = 2 : b = 10;

Or in your case:

condition ? (a = 2, b = 10) : false;

Upvotes: 0

Nina Scholz
Nina Scholz

Reputation: 386624

You need to wrap the assignments in parenthesis and use the comma operator which separates the assignments, instead of semicolon, which separates statements.

The semicolon ends the conditional (ternary) operator ?: before reaching the :, which is a needed part of the syntax and this leads to an error.

let a = 0;
let b = 2;
let condition = true;

condition ? (a = 2, b = 10) : false;

console.log(a, b);

Instead of taking a conditional operator, you could use logical AND &&.

let a = 0;
let b = 2;
let condition = true;

condition && (a = 2, b = 10);

console.log(a, b);

Finally the best approach by using if.

let a = 0;
let b = 2;
let condition = true;

if (condition) {
    a = 2;
    b = 10;
}

console.log(a, b);

Upvotes: 5

Nishant Dixit
Nishant Dixit

Reputation: 5522

let condition1 = false;
let {a=0,b=2} = condition1 ? {a:2,b:10} : {}
console.log(a, b)

let condition2 = true;
let {c=0,d=2} = condition2 ? {c:2,d:10} : {}
console.log(c, d)

Upvotes: 0

ᔕᖺᘎᕊ
ᔕᖺᘎᕊ

Reputation: 3011

Just to give another option not yet posted, if you don't want to use a standard if..else, you could also use ES6's neat destructuring assignment, which is particularly handy if you've already got an array of values that you want to assign from.

For example: (I've used two different conditions to show both outcomes)

let a = 1 > 2 ? [y, z] = [2, 10] : false;
console.log(a); //a = false;

2 > 1 ? [y, z] = [2, 10] : false;
console.log(y, z); //y = 2, z = 10;

Upvotes: 2

Frustrated programmer
Frustrated programmer

Reputation: 711

You cant run more than 1 "line" or "command" (ending with a semicolon) in the ternary operation. You could do 

let condition;
let a = condition ? 2: 0;
let b = condition ? 10 : 2;
console.log(a, b);

which will work for your purpose or if you want to change a and b in a later point

let a = 0;
let b = 0;
let condition;
//later
a = condition ? 2 : a;
b = condition ? 10 : b;

both these examples will work with what you need

Upvotes: 0

Jonas Wilms
Jonas Wilms

Reputation: 138277

Its because of operator predescendence, and the ternary only works with expressions, so might just do:

condition ? ((a = 2), (b = 10)) : false

However, i would prefer:

if(condition) {
 a = 2;
 b = 10;
}

Upvotes: 3

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