目前哪些浏览器支持 JavaScript 的“let"关键字? [英] What browsers currently support JavaScript's 'let' keyword?

问题描述

我正在开发一个应用程序，不必担心 Internet Explorer，并且正在研究 Internet Explorer1 中没有的 A+ 级浏览器中的一些功能.

I'm developing an app and don't have to ever worry about Internet Explorer and was looking into some of the features present in A+ grade browsers that aren't in Internet Explorer1.

我想使用的这些功能之一是 JavaScript 的 let 关键字

One of these features I wanted to play around with is JavaScript's let keyword

我似乎无法让他们的任何让"示例在 Firefox 3.6 中工作(用户代理字符串:Mozilla/5.0(Windows；U；Windows NT 5.1；en-US；rv:1.9.2)Gecko/20100115 Firefox/3.6(.NET CLR 3.5.30729)).我得到 SyntaxError: missing ;执行 let foo = "bar" 时的 before 语句.

I can't seem to get any of their 'let' examples to work in Firefox 3.6 (User-Agent string: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.2) Gecko/20100115 Firefox/3.6 (.NET CLR 3.5.30729)). I get SyntaxError: missing ; before statement when executing let foo = "bar".

那么，哪些浏览器支持 let 关键字?(还是我做错了什么?)

So, what browsers support the let keyword? (Or am I doing something wrong?)

推荐答案

EDIT:所有现代浏览器都支持 let 和 const是 ECMAScript 2015 (ES6)<的一部分/a> 规范.

EDIT: let and const are supported by all modern browsers and are part of the ECMAScript 2015 (ES6) specification.

基本上，如果你不需要支持 IE11 以下的任何东西，let 和 const 现在可以安全使用.

Basically if you don't need to support anything below IE11, let and const are safe to use nowadays.

在 IE11 上，当与 for 循环一起使用时，let 有一个小问题，该变量未绑定到 for 块如您所料，它的行为与 var 一样...

On IE11 there's a small quirk with let when used with for loops, the variable is not bound to the for block as you would expect, it behaves as var did...

另见:let 和 const 支持.

2010 年的旧答案:这些扩展不是 ECMA 标准的，只有 Mozilla 实现支持它们.

Old and outdated answer from 2010: Those extensions are not ECMA-Standard, they are supported only by the Mozilla implementation.

在浏览器环境中，您应该在 script 标签中包含 JavaScript 版本号以使用它:

On browser environments you should include the JavaScript version number in your script tag to use it:

<script type="application/javascript;version=1.7">  
  var x = 5;
  var y = 0;

  let (x = x+10, y = 12) {
    alert(x+y + "
");
  }

  alert((x + y) + "
");
</script>

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