jQuery如何完成命令的链接？ [英] How does jQuery accomplish chaining of commands?

问题描述

我认为自己（充其量）是一个中级JavaScript家伙......当然......我想了解一些事情已经完成，所以我可以编写更好的代码。因此，我一直在寻找jQuery的内幕，试图更多地了解某些事情是如何完成的。

I consider myself (at best) a mid-level JavaScript guy...and of course...I want to understand HOW some things are accomplished so I can write better code. As such, I've been looking under-the-hood of jQuery trying to uderstand it a little more about how certain things are accomplished.

例如：

jQuery处理IE和Opera按名称而不是ID返回项目的情况：

For example:
jQuery handles the case where IE and Opera return items by name instead of ID by doing the following:

// HANDLE: $("#id")
else 
{
    var elem = document.getElementById( match[3] );

    // Handle the case where IE and Opera return items
    // by name instead of ID
    if ( elem && elem.id != match[3] )
        return jQuery().find( selector );

    // Otherwise, we inject the element directly into the jQuery object
    var ret = jQuery( elem || [] )
    ret.context = document;
    ret.selector = selector;

    return ret;
}

...好的，这很简单！

...okay that's easy!

但是一个典型的jQuery代码链将一系列命令链接在一起：

$('#someElementId').fadeIn().css({ ...Some CSS Properties ... });

现在......我认为'链接部分是在以下区域处理的：

Now...I 'think' the chaining portion is handled in the following area:

jQuery.extend = jQuery.fn.extend = function() { ... };

我正在梳理这个区域......我看到单身如何命令被处理...但我没有真正看到WHERE或如何管理命令链。所以我显然错过了一些东西。

I'm combing through this area...and I see HOW a single command is processed...but I don't really see WHERE or HOW a chain-of-commands are managed. So I am obviously missing something.

所以我的问题是：

1. jQuery如何实现选择器的链接？

推荐答案

根据你的评论：

这是来自这里的例子： http://en.wikipedia.org/wiki/Fluent_interface#JavaScript
附加评论

This is from the example here: http://en.wikipedia.org/wiki/Fluent_interface#JavaScript With extra comments

var Car = function() {

        var speed, color, doors;

        this.setSpeed = function(speed) {
                this.speed = speed;
                **//Returns the reference to the calling `car` object** 
                return this; 
        };

        this.setColor = function(color) {
                this.color = color;
                **//Returns the reference to the calling `car` object** 
                return this; 
        };

        this.setDoors = function(doors) {
                this.doors = doors;
                **//Returns the reference to the calling `car` object** 
                return this; 
        };

};

// Fluent interface
**//Each method returns a reference to the object itself**
**//so the next method chain is refering back to the previous returned value**
**//ie - itself, the orginal object that started the call chain**
myCar = new Car();
myCar.setSpeed(100).setColor('blue').setDoors(5);

// Example without fluent interface
**// normal, non fluent style, where each method returns Void**
**// so you need to start with the object reference yourself each time**
myCar2 = new Car();
myCar2.setSpeed(100);
myCar2.setColor('blue');
myCar2.setDoors(5);

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