Conditional statement after the Or operator in JavaScript

Question

In JavaScript, is it possible to place a Conditional statement after an Or operator? If so, why is the following fails for me?

var value = 1 || true ? 2 : 3;    // equals to 2

When I set value to be equals to [1 || true ? 2 : 3], I get an unexpected result. The result that get is that:

value == 2

I've expected value to be equals to 1 (value= = 1), since 1 is truthy, and the Or statement should have return 1. The conditional statement is not even supposed to be executed.

The only way val can be equals to 2 (val == 2) is if the Or operator is behaving not as expected, and runs the second part of the Or statement and the Conditional statement that is in it.

Why is it behaving that way?

Because it's interpreted as (1 || true) ? 2 : 3

haim770
– haim770

2017-01-16 19:33:47 +00:00
Commented Jan 16, 2017 at 19:33 — haim770
– haim770, Commented Jan 16, 2017 at 19:33
Ohh.. I forgot about operator precedence ..

Guy Eizon
– Guy Eizon

2017-01-16 19:36:28 +00:00
Commented Jan 16, 2017 at 19:36 — Guy Eizon
– Guy Eizon, Commented Jan 16, 2017 at 19:36

T.J. Crowder · Accepted Answer · 2017-01-16 19:34:53Z

3

I've expected value to be equals to 1 (value = 1), since 1 is truthy

To get that, you need parens:

var value = 1 || (true ? 2 : 3);
// --------------^------------^

Without them, the || is between 1 and true, and then the conditional operator's first operand is the result of that (which is 1).

This is because || has higher precedence than the conditional operator (just); here's a table on MDN.

answered Jan 16, 2017 at 19:34

T.J. Crowder

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Comments

haim770 · Accepted Answer · 2017-01-16 19:38:43Z

0

Because Logical OR has precedence over the Conditional operator. Then your statement is actually interpreted as:

(1 || true) ? 2 : 3;

Which obviously evaluates to 2.

See MDN

edited Jan 16, 2017 at 19:38

answered Jan 16, 2017 at 19:36

haim770

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1 Comment

Guy Eizon Over a year ago

Thank you guys for the fast response (:

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