数组像JavaScript对象 [英] Array Like Objects in Javascript
问题描述
我想知道的jQuery如何构建它的阵列状物体。我试图找出最关键的事情是如何设法得到控制台间preT它作为一个数组,并显示它是这样。我知道它是与length属性,但打了一下后,我不能完全弄清楚。
I'm wondering how jQuery constructs its array-like object. The key thing I'm trying to work out is how it manages to get the console to interpret it as an array and display it as such. I know it has something to do with the length property, but after playing a bit I can't quite figure it out.
我知道这已超过正常的阵列状物体没有技术优势,如下面的例子。但我认为这是一个重要的语义元素时用户测试和调试。
I know this has no technical advantage over a normal array like object as in the example below. But I think it's an important semantic element when users are testing and debugging.
一个普通阵列状物体。
function foo(){
// Array like objects have a length property and it's properties use integer
// based sequential key names, e.g. 0,1,2,3,4,5,6 just like an array.
this.length = 1;
this[0] = 'hello'
}
// Just to make sure add the length property to the prototype to match the Array
// prototype
foo.prototype.length = 0;
// Give the Array like object an Array method to test that it works
foo.prototype.push = Array.prototype.push
// Create an Array like object
var bar = new foo;
//test it
bar.push('world');
console.log(bar);
// outputs
{ 0: 'hello',
1: 'world',
length: 2,
__proto__: foo
}
在哪里为jQuery的将输出
Where as jQuery would output
var jQArray = $('div')
console.log(jQArray);
// outputs
[<div></div>,<div></div>,<div></div>,<div></div>]
如果您运行
console.dir(jQArray)
// Outputs
{ 0: HTMLDivElement,
1: HTMLDivElement,
2: HTMLDivElement,
3: HTMLDivElement,
4: HTMLDivElement,
context: HTMLDocument,
length: 5,
__proto__: Object[0]
}
jQuery对象的原型是因为它的对象特别有意思,而不是jQuery.fn.init正如所预料的,也是[0]表示的东西,因为这是你得到你想要的时候。
The proto of the jQuery object is especially interesting since its the Object and not jQuery.fn.init as would be expected, also the [0] indicates something as this is what you get when you.
console.dir([])
// outputs Array[0] as the object name or Array[x] x being the internal length of the
// Array
我不知道的jQuery是如何设置它的原型为对象[0]但我的猜测是,答案就在那里的某个地方。任何人有什么想法?
I have no idea how jQuery has set it's proto to be Object[0] but my guess is that answer lies somewhere in there. Anyone got any ideas?
推荐答案
对象必须具有长度
和拼接
> var x = {length:2, '0':'foo', '1':'bar', splice:function(){}}
> console.log(x);
['foo', 'bar']
和供您参考,对象[0]
为原型是完全一样的道理。浏览器看到的原型本身作为一个数组,因为:
and FYI, the Object[0]
as the prototype is for exactly the same reason. The browser is seeing the prototype itself as an array because:
$.prototype.length == 0;
$.prototype.splice == [].splice;
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