JQuery and JavaScript methods

Question

In majority of JavaScript method(iterator) callback first argument is element and second is index. But in case of jQuery always second argument is element and first one is index. Why they formatted differently? Is that for avoiding confusion between them, since both contains methods like map, filter, etc. Is there any special meaning behind that? I'm just curious to know.

No, there isn't. jQuery is a rebel in this case. See arguments of $.map and $.fn.map callbacks. — Ram
– Ram, Commented Jun 23, 2016 at 3:11
@Vohuman : yup, in case $.map first argument is value... i didn't noticed that :) — Pranav C Balan
– Pranav C Balan, Commented Jun 23, 2016 at 3:24
Because you didn't expect it. This is an inconsistency and a confusing feature. — Ram
– Ram, Commented Jun 23, 2016 at 3:31
@Vohuman : yes, you are right.... when I started working in jQuery it's always confused me..... — Pranav C Balan
– Pranav C Balan, Commented Jun 23, 2016 at 3:33

BotNet · Accepted Answer · 2016-06-23 03:30:28Z

2

This is because jQuery relies on this; it doesn't need an element iterator.

$('selector').each(function(){
  // 'this' refers to unwrapped jQuery selector element; no need for arguments == cleaner code
  var $this = $(this);
});

In Vanilla JS, iterators rely on the parameters:

[].forEach(function(el, index){
   // 'this' refers to Window object; use the argument
   el.querySelector('foo')
});

Because jQuery can utilize the scoped element using this, it doesn't really need the arguments. I'd have to look up the history of the library to even see if the element existed as the second argument in earlier versions.

edited Jun 23, 2016 at 3:30

answered Jun 23, 2016 at 3:12

BotNet

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15 Comments

guradio Over a year ago

can you elaborate more on the answer. this one is not clear this is more like a comment

BotNet Over a year ago

@guradio if you chill out the answer will be updated ;)

Pranav C Balan Over a year ago

yup that may be a reason, so the value arg doesn't have that much importance here :)

guradio Over a year ago

i was too excited to know mate :)

BotNet Over a year ago

@guradio that sounded more snappy than intended, I've had a couple drinks and am laughing

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