在创建JavaScript数组状物体 [英] Creating array-like objects in JavaScript

问题描述

在JavaScript中，有对象pretend是阵列（或属于阵列状）。这样的对象是参数，节点列表 S（从 getElementsByClassName 返回等），和jQuery对象

In JavaScript, there are objects that pretend to be arrays (or are "array-like"). Such objects are arguments, NodeLists (returned from getElementsByClassName, etc.), and jQuery objects.

在的console.log GED，他们似乎阵列，但他们不是。我知道，为了要阵列状，一个对象必须有一个长度属性。

When console.logged, they appear as arrays, but they are not. I know that in order to be array-like, an object must have a length property.

所以我做了一个对象是这样的：

So I made an "object" like this:

function foo(){
    this.length = 1;
    this[0] = "bar";
}

var test = new foo;

当我控制台日志（测试），我得到（预期）一个富对象。我可以使用转换它一个数组

When I console log(test), I get (as expected) a foo object. I can "convert" it to an array using

Array.prototype.slice.call(test)

不过，我不希望把它转换，我想这是阵列等。如何使类似数组的对象，这样，当它的的console.log GED，它显示为一个数组？

But, I don't want to convert it, I want it to be array-like. How do I make an array-like object, so that when it's console.logged, it appears as an array?

我试着设置 foo.prototype = Array.prototype ，但的console.log（新富）仍显示一个富的对象，而不是一个数组。

I tried setting foo.prototype = Array.prototype, but console.log(new foo) still shows a foo object, and not an array.

推荐答案

取决于具体的控制台上。对于Chrome的开发者控制台自定义对象和Firebug的，你需要两个长度和拼接属性。 拼接也必须是一个函数。

Depends specifically on the console. For custom objects in Chrome's developer console, and Firebug you'll need both the length and splice properties. splice will also have to be a function.

a = {
    length: 0,
    splice: function () {}
}
console.log(a); //[]

要注意这一点很重要，但是，没有官方的标准。

It's important to note, however, that there is no official standard.

以下code用于的jQuery（v1.11.1）在内部确定对象是否应该使用为环或的for..in 循环：

The following code is used by jQuery (v1.11.1) internally to determine if an object should use a for loop or a for..in loop:

function isArraylike( obj ) {
    var length = obj.length,
        type = jQuery.type( obj );

    if ( type === "function" || jQuery.isWindow( obj ) ) {
        return false;
    }

    if ( obj.nodeType === 1 && length ) {
        return true;
    }

    return type === "array" || length === 0 ||
        typeof length === "number" && length > 0 && ( length - 1 ) in obj;
}

请注意，它是可能有，在控制台显示为一个数组（ [] ），但被遍历了的对象..in 循环jQuery中，或者出现在控制台中的对象的对象（ {} ），但被遍历以在jQuery的循环。

Note that it's possible to have an object that appears in the console as an array ([]) but that gets iterated over with a for..in loop in jQuery, or an object that appears as an object in the console ({}) but that gets iterated over with a for loop in jQuery.

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