Assign a value to different variable based on a certain condition

Question

How can I assign a value to different variable based on a certain condition?

For example, if now the variable a is true, then I want to assign the string "Hello" to the variable b, but not the variable c.

But if now the variable a is not true, then I hope the string "Hello" could be assigned to the variable c, but not the variable b.

Is there a way to assign a value to different variable based on a certain condition in Javascript?

Like this:

var a = true;
var b, c;
((a) ? b : c) = "Hello";
console.log(b); //This should output "Hello"
console.log(c); //This should output `undefined`

AGA · Accepted Answer · 2019-04-28 16:02:52Z

0

Try an if... else statement.

var a = true;
var b, c;
if (a) {
  b = "Hello";
} else {
  c = "Hello";
}
console.log(b); //This should output "Hello"
console.log(c); //This should output `undefined`

answered Apr 28, 2019 at 16:02

AGA

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Comments

Bergi · Accepted Answer · 2019-04-28 16:10:06Z

No, you cannot choose the target of an assignment as an expression¹. You should just write

if (a) {
    b = "Hello";
} else {
    c = "Hello";
}

If you don't want to duplicate the "Hello" expression that constructs the variable, put it in a temporary variable. However it is really rare that you need to assign to different variables. Consider calling a function instead which has the result you want based on your condition:

function chooseOrder(x) {
    return a ? [x, undefined] : [undefined, x];
}
;[b, c] = chooseOrder("Hello");

1: well, there's always an exception. We could for example use setter properties, and dynamically choose the object whose property is assigned:

(a
  ? {set value(v) { b = v; }}
  : {set value(v) { c = v; }}
).value = "Hello";

but this really should be considered a trick with a temporary variable.

Pierce Griffiths · Accepted Answer · 2019-04-28 17:06:30Z

0

You cannot choose the target of an assignment using an expression. An if() ... else is needed for what you're trying to do.

var a = true;
var b, c;
if(a)
  b = "Hello";
else
  c = "Hello";
console.log(b);
console.log(c);

edited Apr 28, 2019 at 17:06

answered Apr 28, 2019 at 16:04

Pierce Griffiths

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