js的官方文档网站：
https://developer.mozilla.org/
js版本介绍的文章：
https://www.w3schools.com/js/js_versions.asp
toString()用法：
想在html里面使用最新的js版本：
https://developer.mozilla.org/en-US/docs/Archive/Web/JavaScript/New_in_JavaScript/1.8
42
Wikipedia (or rather, the community on Wikipedia) keeps a pretty good up-to-date list here.
Most browsers are on 1.5 (though they have features of later versions)
Mozilla progresses with every dot release (they maintain the standard so that's not surprising)
Firefox 4 is on JavaScript 1.8.5
The other big off-the-beaten-path one is IE9 - it implements ECMAScript 5, but doesn't implement all the features of JavaScript 1.8.5 (not sure what they're calling this version of JScript, engine codenamed Chakra, yet).
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查看各个浏览器的javascript版本的方法:
https://stackoverflow.com/questions/4271566/how-do-i-know-which-version-of-javascript-im-using
新建一个html页面，用各个浏览器打开即可：
1. chrome:
2. firefox
3. ie
4. edge
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1. javascript or ECMAscript
netscape
JavaScript was invented by Brendan Eich in 1995, and became an ECMA standard in 1997.
ECMAScript is the official name of the language.
From 2015 ECMAScript is named by year (ECMAScript 2015).
JavaScript was developed for Netscape. Netscape 2 was the first browser to run JavaScript.
After Netscape the Mozilla foundation continued to develop JavaScript for the Firefox browser.
The latest JavaScript version was 1.8.5. (Identical to ECMAScript 5).
ECMAScript was developed by ECMA International after the organization adopted JavaScript.
The first edition of ECMAScript was released in 1997.
This list compares the version numbers of the different products:
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