是什么让 jQuery 对象在 Chrome 的开发人员工具中显示为数组? [英] What makes a jQuery object show up as an array in Chrome's Developer Tools?

问题描述

我想知道 jQuery 对象如何在 Chrome 开发者工具的控制台日志中显示为数组.

I'm wondering how it's possible that jQuery objects show up as an array in the console log of Developer Tools in Chrome.

例如如果我执行 $('<a>')，我在控制台日志中看到的是:

E.g. if I execute $('<a>'), what I see in the console log is:

[<a>​</a>​]

但下列说法是错误的:

var a = $("<a>");

Array.isArray(a);   // false
a instanceof Array; // false

我尝试修改 jQuery 并查看会发生什么，令人惊讶的一件事是从 jQuery 函数中删除 length 会删除数组符号:

I tried to modify jQuery and see what happens, and one thing that was surprising is that removing length from the jQuery function removes the array notation:

length: 0, // commenting this line removes array notation

相反，它然后显示为(箭头是要展开的实心):

Instead, it then shows up as (arrow is that solid one to expand):

> jQuery.jQuery.fn.jQuery.init

但是，如果我尝试制作应该以数组表示法显示的自己的构造函数，则它不起作用:

But, if I try to make my own constructor which is supposed to be displayed in array notation, it does not work:

var test = function() { this.length = 0 };

new test();

// Logged (arrow is same one as before):
// > test

所以我想知道在 jQuery 代码中是什么让开发人员工具将实例显示为数组.jQuery 中添加了哪些属性/功能/事物，使开发人员工具在显示实例时将其作为数组处理?

So I'm wondering what in the jQuery code makes Developer Tools show instances as an array. What property/function/thing is added to jQuery that makes Developer Tools handle it as an array when displaying an instance?

推荐答案

来自 http://api.jquery.com/jQuery.makeArray/:

jQuery 和 JavaScript 中的许多方法通常返回类似数组的对象.例如，jQuery 工厂函数 $() 返回一个 jQuery 对象，该对象具有数组的许多属性(长度、[] 数组访问运算符等)，但与数组并不完全相同，并且缺少一些数组的内置方法(例如 .pop() 和 .reverse()).

Many methods, both in jQuery and in JavaScript in general, return objects that are array-like. For example, the jQuery factory function $() returns a jQuery object that has many of the properties of an array (a length, the [] array access operator, etc.), but is not exactly the same as an array and lacks some of an array's built-in methods (such as .pop() and .reverse()).

基本上，对象必须具有 length 和 splice 属性才能像数组一样.这是一个相关的 SO 问题:Javascript 中的类似数组的对象

Basically, The object has to have length and splice properties to be array-like. Here is a relevant SO question: Array Like Objects in Javascript

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