几年前我做了一些javascript/jQuery编程，然后我又重新开始了.当时所有jQuery功能都使用美元符号，如果没有导入jQuery库，则没有定义美元符号.
今天，我启动了Firefox，在一个完全空的html文件中，没有javascript库，但美元符号指向一些东西.如果我打开Firefox控制台并键入'$'，我会得到"function()".
1) Is it correct that dollar sign was not assigned, a few years back, or do I remember wrong?
2) What is the dollar sign, if not jQuery?
1) 几年前没有指定美元符号是对的，还是我记错了？
那是正确的，而且仍然是正确的.
2)如果不是jQuery，美元符号是什么？
Firefox和Chrome实现$、$$和其他几个辅助命令.两者都将设置为$$到document.querySelectorAll()，如果尚未定义window.$，则将设置为$到document.querySelector.
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.