"Go" jQuery with $ (function () {}) and (function ($) {}) (jquery), $ (document). The difference between ready (function () {}) is explained in detail

1, (function ($) {...}) (JQuery);

1), principle:

This is actually an anonymous function, as follows:

Function (ARG) {...}
This defines an anonymous function with a parameter of ARG

When calling a function, the parentheses and arguments are written after the function, and because of the precedence of the operator, the function itself needs parentheses, namely:
(function (ARG) {...}) (param)
This is equivalent to defining an anonymous function with a parameter of ARG, and calling this anonymous function as a parameter param

and (function ($) {...}) (jquery) is the same, the reason why only use $ in formal parameters is to not conflict with other libraries, so the argument with JQuery
Equivalent to funtion output (s) {...};output (jQuery), or Var fn=function (s) {...}; FN (jQuery);

2), function (very useful):

The greatest benefit of this notation is the formation of closures. In (function ($) {...}) (jQuery) functions and variables defined internally can only be valid within this scope.

The concept of whether a function function or a private variable is formed. Like what:

var i=3;function init () {    alert ("Outer init:" +i);} (function ($) {var i=2;function init () {    alert ("Inner init:" +i);} Init ();}) (jQuery); init ();

Execution Result:

Inner Layer Init:2

Outer Init:3

2, $ (function () {...});  JQuery (function ($) {...}); $ (document). Ready (function () {...})

The effect of these three is the same, I need to use the first type, writing simple.

A function that executes after the document is loaded.

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"Go" jQuery with $ (function () {}) and (function ($) {}) (jquery), $ (document). The difference between ready (function () {}) is explained in detail