How can I alert supported EcmaScript version of the browser?

Question

有没有办法提醒我运行JavaScript的当前环境支持的EcmaScript版本？

Answer 1

Short answer : No.

Long answer : First of all, browsers doesn't implement ECMAScript but a language based on that specification (eg JavaScript for Firefox, JScript for Microsoft). Often, they can implement part of the standard, and complete the standard in a next version of the language (it happened in JavaScript 1.8 / 1.8.1 / 1.8.5 about ES5 for example, see New in JavaScript ).

Plus, they could anticipate the standard: see for...of or let , that Mozilla has since years, that are part of ES6.

So, you can't really say what ES version is supported by your environment; what you can do is testing the functionality you are interested in, and use them. In most of the case, we apply a shim, where is possible, to emulate that functionality, like for ES5 .