jQuery:$ .when的行为根据参数数量而有所不同 [英] Jquery: $.when behaves differently depending on number of arguments

问题描述

$.何时行为取决于是否将一个或多个Deferred对象传递给它.此行为已在文档中进行了记录-但问题是它迫使我编写了两个不同的代码路径.

$.when behaves differently depending on whether one or more Deferred object are passed to it. This behaviour is documented in the docs - but the problem is that it is forcing me to write two different code paths.

function foo (dfds) {
    $.when.apply(this, dfds).done(function() {
        console.log(arguments);
    });
}

案例1:

foo([$.getJSON("http://freegeoip.net/json/8.8.8.8"),
     $.getJSON("http://freegeoip.net/json/8.8.8.9")]);
....
/* Output (what I'd come to expect) */
[Array[3], Array[3]]

第二种情况:

foo([$.getJSON("http://freegeoip.net/json/8.8.8.8")]);
....
/* Output (the original unwrapped deferred's arguments) */
[Object, "success", Object]

有什么方法可以优雅地处理此问题而无需检查dfd的长度或arguments的类型?

Any way to elegantly handle this without resorting to checking the length of dfd or the type of arguments?

推荐答案

我认为您不能避免显式测试延迟对象的数量.假设您要返回延迟的对象:

I don't think you can avoid explicit testing the number of deferred objects. Assuming you want to return the deferred object:

function foo (dfds) {
    if(dfds.length > 1) {
        return $.when.apply(this, dfds);
    }
    else {
        return dfds[0].pipe(function() {
            return [Array.prototype.slice.call(arguments, 0)]
        });
    }
}

您可以创建一个jQuery插件来包装此功能并使其可重用:

You could create a jQuery plugin to wrap this functionality and make it reusable:

(function($) {
    $.when_ = function() {
        if(arguments.length > 1) {
            return $.when.apply(this, arguments);
        }
        else {
            return arguments[0].pipe(function() {
                return [Array.prototype.slice.call(arguments, 0)];
            });
        }
    };
}(jQuery));

您也可以覆盖$.when，但是我不确定是否在内部使用它.

You could also override $.when but I don't know for sure whether it is used internally or not.

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