Strange javascript syntax

Question

anybody can help me with the following Js syntax? I don't understand the line starting with "( $.inArray( wzdId, this...." I mean why does that line start with just a parentesis? What does it mean?

This is the complete code:

_activateStep: function( wzdId ) {
  if ( condition ) {
    var stepIndex = this._findNav( wzdId ).index(); 
    for( var i = 0; i < stepIndex; ++i) { 
      if( condition ) === -1 ) {
        return;
      }
    }
    ( $.inArray( wzdId, this._activatedSteps ) === -1 ) && this._activatedSteps.push( wzdId );
  }
}

Thank you

The parenthesis ((...)) in this case are the grouping operator. You can use it to change the order of precedence or just make expressions more readable. For example: 6 * (4 + 3) or (5 * 2) + (4 * 8). — Felix Kling
– Felix Kling, Commented Apr 5, 2013 at 17:49

Denys Séguret · Accepted Answer · 2013-04-05 17:34:03Z

6

what you have here is

A && B

It uses a common trick based on short-circuit logical operators : B is executed only if A is true.

That's another way to write

if (A) B;

Some people like it because it's a little shorter. It's obviously much less readable too.

answered Apr 5, 2013 at 17:34

Denys Séguret

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4 Comments

rlemon Over a year ago

the braces can be around either of the statements. afaik. I often A && (B) myself.

Chad Over a year ago

I use the OR (||) operator to set defaults like var a = yourPassVal || 0, but you have to be careful for when a falsey value is allowed and your default isn't it.

rlemon Over a year ago

and you can do so much fun stuff with it example from another answer

Alessio De Feudis Over a year ago

Clear and quick! Thanks to all of you for your help!

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