CODEWITHSUNDEEP
javascriptjquerymobileif-statementtouch
cpk
cpk

Reputation: 809

Explanation of touch event jQuery function

I wrote a function that works great for mobile, based on something I found on SO a while ago. 

    jQuery(document).on('touchstart', function(event) {
        if ( !jQuery(event.target).closest("#peopleMenu").length) {
            jQuery("#peopleMenu").fadeOut();
       } 
    });

the part that I found was in the "if" statement that took me a bit to wrap my head around.

It is saying that if the target touch event is on #peopleMenu , it will stay open, or close if touched off. The if statement boils down to :

if (!1) {
    //false - understand this.
}

if (!0) {
    //true - hmmm.
}

My question is basically is this a common programming paradigm, a strange js feature, or is it just trickier than it needs to be? Thanks.

Upvotes: 0

Views: 52

Answers (2)

Karl-André Gagnon
Karl-André Gagnon

Reputation: 33880

It is common, it mean if you touch something else than #peopleMenu or its childrens, do something.

0 is a falsy value while every other integer are truthy.

Using bang (!) reverse the value, !true == false and !false == true.

The .length property of jQuery is the way to know how many element are selected. 0 mean none.

Upvotes: 1

binaryatrocity
binaryatrocity

Reputation: 976

This is common in many languages. Everything in JavaScript has an inherent Boolean value, generally known as either truthy or falsy.(e.g. 0 or an empty string). So in this case, if the length comes back as 0, the if statement is false. Here is a great writeup on this topic as it relates to Javascript if you care to know more: Truthy/Falsy

Upvotes: 1

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