如果不是jQuery，Javascript中的美元符号是什么？ [英] What is the dollar sign in Javascript, if not jQuery

问题描述

几年前我做了一些javascript / jQuery编程，我刚刚重新开始。当时美元符号用于所有jQuery功能，如果没有导入jQuery库，则未定义美元符号。

I did some javascript / jQuery programming a few years ago, and I just started up again. Back then the dollar sign was used for all the jQuery functionality, and if no jQuery library was imported, the dollar sign was not defined.

今天，我在一个没有javascript库的完全空的html文件中启动了Firefox，但是美元符号指向某个东西。如果我打开Firefox控制台并输入'$'，我会得到function（）。

Today, I started up Firefox, in a completely empty html file with no javascript libraries, and yet the dollar sign points to something. If I open the Firefox console and type '$' I get "function()".

1）几年前没有分配美元符号是正确的，还是我记错了？

1) Is it correct that dollar sign was not assigned, a few years back, or do I remember wrong?

2）是什么美元符号，如果不是jQuery？

2) What is the dollar sign, if not jQuery?

推荐答案

1）美元是否正确标志没有分配，几年前，还是我记得错了？

1) Is it correct that dollar sign was not assigned, a few years back, or do I remember wrong?

这是正确的，仍然是真的。

That's correct and still true.

2）如果不是jQuery，美元符号是多少？

2) What is the dollar sign, if not jQuery?

Firefox 和 Chrome 实现 $ ， $$ 和其他几个作为帮助程序命令。两者都将 $$ 设置为 document.querySelectorAll（），并设置 $ 到 document.querySelector 如果窗口。$ 尚未定义。

Firefox and Chrome implement $, $$ and several others as helper commands. Both will set $$ to document.querySelectorAll(), and set $ to document.querySelector if window.$ hasn't been defined.

所以你所看到的实际上并不是标准的JavaScript，而是浏览器开发者控制台中的助手。它也不是jQuery（只要你不在使用jQuery的页面上）。但是，它的行为接近 jQuery 的行为，关于 querySelector （对于单个匹配）和 querySelectorAll （对于多个匹配）提供与jQuery选择器几乎相同的强度。

So what you're seeing isn't actually standard JavaScript, but a helper in the developer console of your browser. It's also not jQuery (as long as you're not on a page using jQuery). However, it's behaviour is close to the one of jQuery, concerning that querySelector (for single matches) and querySelectorAll (for multiple matches) give you almost the same strength as the jQuery selector.

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