Please explain this line of javascript code

Question

jBox.prototype.position = function (options)
{
  // this line
  !options && (options = {});

}

In conventional programming boolean statements are used in if else statements. What does !options && (options = {}); translate too?

options is a json or array. What does !options mean?

options = {} is assigning a empty json to variable options, how does it return a boolean value to be used with &&.

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Logical_Operators — Teemu, Aug 13 '18 at 09:28
You might want to look up each individual thing you don't understand. https://developer.mozilla.org/en-US/ is a good place to start — evolutionxbox, Aug 13 '18 at 09:28
"how does it return a boolean value to be used with &&" — `&&` doesn't operate on boolean values — Quentin, Aug 13 '18 at 09:29
I somehow find `options = options || {}` to be more readable. — Robby Cornelissen, Aug 13 '18 at 09:29
Careful with the terminology. `{}` is not a "json", it's an object literal. — Sergio Tulentsev, Aug 13 '18 at 09:30
@RobbyCornelissen — I'd just use a default argument value these days. — Quentin, Aug 13 '18 at 09:30
@Quentin: in javascript, does the default argument value protect from a falsey value being explicitly passed? `position('')`. Subtle difference, but matters sometimes. — Sergio Tulentsev, Aug 13 '18 at 09:33

score 2 · Accepted Answer · answered Aug 13 '18 at 09:28

2

The code:

!options && (options = {});

is the equivalent of:

if(!options) { 
    options = {}; 
}

answered Aug 13 '18 at 09:28

Faly

score 0 · Answer 2 · answered Aug 13 '18 at 09:28

0

It means that if options is a falsy value (empty) then initialize it with an empty object literal.

answered Aug 13 '18 at 09:28

void

2 Answers2