使用jQuery.extend覆盖函数的原因可能是什么? [英] What might be a reason of overriding function using jQuery.extend?

问题描述

我在寻找扩展Bootstrap插件的正确方法，并找到了以下答案: https://stackoverflow.com/a/12689534/1276032

I was searching for a proper way of extending bootstrap plugin, and found this answer: https://stackoverflow.com/a/12689534/1276032

困扰我的是最后一部分-初始化覆盖.复制的代码如下:

What troubles me, is the last section - initialization overriding. Copied code below:

// override the old initialization with the new constructor
$.fn.modal = $.extend(function(option) {

    var args = $.makeArray(arguments),
        option = args.shift();

    return this.each(function() {

        var $this = $(this);
        var data = $this.data('modal'),
            options = $.extend({}, _super.defaults, $this.data(), typeof option == 'object' && option);

        if ( !data ) {
            $this.data('modal', (data = new Modal(this, options)));
        }
        if (typeof option == 'string') {
            data[option].apply( data, args );
        }
        else if ( options.show ) {
            data.show.apply( data, args );
        }
    });

}, $.fn.modal);

我不明白为什么在这种情况下使用$ .extend －它会产生一些我看不到的效果吗?如果我执行以下代码:

I don't understand why $.extend is used in this case - does it have some effect that I don't see? If I execute this code:

var f1 = function(){console.log(1);};
var f2 = function(){console.log(2);};
var f2 = $.extend(f1,f2);
f2();

然后只有1打印到控制台，并且f1等于f2.这样看来，简单的拼命就可以了，

then only 1 is printed to the console, and f1 equals f2. So it seems simple assingnment would do,

$.fn.modal = function(option) {...}

但是也许我想念一些东西...

but maybe I miss something...

推荐答案

您需要更改此设置:

$.fn.modal = $.extend(function(option) {
    // your code ...
}, $.fn.modal);

为此:

$.extend($.fn.modal, function(option) {
    // your code ...
});

TL; DR

$.extend(a, b)将 b 的内容复制到 a (修改其内容)上，如果重复，则 b 仍然存在.同样，它返回 a 的值.

$.extend(a, b) copies the content of b on a (modifying it's content), and if any repeated, then the property of b remains. Also, it returns the value of a.

所以，如果您有这个:

hello    = { unique_on_hello: 'hola',  message: 'hello message' }
world    = { unique_on_world: 'mundo', message: 'WORLD MESSAGE' }
response = $.extend(hello, world)

每个值将为:

hello    // {unique_on_hello: "hola", message: "WORLD MESSAGE", unique_on_world: "mundo"}
world    // {unique_on_world: "mundo", message: "WORLD MESSAGE"}
response // {unique_on_hello: "hola", message: "WORLD MESSAGE", unique_on_world: "mundo"}

因此，如果您执行 f2 = $.extend(f1,f2);与相同:

So, if you do f2 = $.extend(f1,f2); is the same as:

$.extend(f1, f2) // Copy properties of f2 to f1
f2 = f1

来源: https://api.jquery.com/jquery.extend/

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