A brief analysis of jQuery's initialization and object construction_jquery

To summarize:

1. The entire class library is defined in an anonymous function, eliminating the generation of global variables;
2. Passing undefined as a missing parameter prevents the pollution of undefined variables;
3. It can be seen that $(...) actually returns an instance of the jQuery.fn.init object, and then points the prototype of the object to jQuery.prototype (statement jQuery.fn.init.prototype = jQuery.fn ), so the generated instances share the methods and properties in jQuery.prototype and implement chain programming operations;
4. Finally, export jQuery and $ as global variables through window.jQuery = window.$ = jQuery.

Copy code The code is as follows:

(function(window, undefined) {
// Define a local copy of jQuery
var jQuery = (function() {
var jQuery = function(selector, context) {
// The jQuery object is actually just the init constructor 'enhanced '
return new jQuery.fn.init(selector, context/*, rootjQuery*/);
};
// ...
jQuery.fn = jQuery.prototype = {
constructor : jQuery,
init : function(selector, context, rootjQuery) {
// ...
}
// ...
};
// Give the init function the jQuery prototype for later instantiation
jQuery.fn.init.prototype = jQuery.fn;
// ...
// Expose jQuery to the global object
return jQuery;
})();
// ...
window.jQuery = window.$ = jQuery;
})(window);