CODEWITHSUNDEEP
javascriptjquery
Alexander Solonik
Alexander Solonik

Reputation: 10230

understanding complex if condition in modal.js

hey guys i was just going through the source if modal.js and came across the following line : 

if (!that.$element.parent().length) {

  }

i am new to JS and Jquery in general , what i figure is the not operator is being used here and basicall we are getting the parent element of $element and then accessing the length property . but i still don't quite get the practical usage of this condition .

This condition can be seen on line 79 , on git too .

Thank you.

Alex-Z .

Upvotes: 0

Views: 50

Answers (2)

Alex
Alex

Reputation: 21766

It checks if the given element already exists in the the DOM. This logic ensures it will not be added twice:

 if (!that.$element.parent().length) {
    that.$element.appendTo(that.$body) // don't move modals dom position
  }

Upvotes: 1

Andreas Berheim Brudin
Andreas Berheim Brudin

Reputation: 2290

That is basically checking if such an element exists. Every JQuery selector implicitly returns a list of elements, which can be empty. If length is 0, this will evaluate to false in a boolean context, so ! in front will make this condition true if the element does not exist (element list is empty).

Upvotes: 1

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