Узнать стандарт JS

        <script type="text/javascript">var jsver = 1.0;</script>
        <script language="Javascript1.1">jsver = 1.1;</script>
        <script language="Javascript1.2">jsver = 1.2;</script>
        <script language="Javascript1.3">jsver = 1.3;</script>
        <script language="Javascript1.4">jsver = 1.4;</script>
        <script language="Javascript1.5">jsver = 1.5;</script>
        <script language="Javascript1.6">jsver = 1.6;</script>
        <script language="Javascript1.7">jsver = 1.7;</script>
        <script language="Javascript1.8">jsver = 1.8;</script>
        <script language="Javascript1.9">jsver = 1.9;</script>
        <script type="text/javascript">
          console.log(" js-version="+jsver+" (1.7=Baidu=Chromium) ");
        </script>

function check_ES6() {
    "use strict";
    if (typeof Symbol == "undefined") return false;
    try {
        eval("class Foo {}");
        eval("var bar = (x) => x+1");
    } catch (e) { return false; }
    return true;
}
if (check_ES6()) {
    // The engine supports ES6 features you want to use
    var s = document.createElement('script');
    s.src = "es6script.js";
    document.head.appendChild(s);
} else {
    // The engine doesn't support those ES6 features
    // Use the boring ES5 :(
}

(function() {
  var v8string = 'function%20javaEnabled%28%29%20%7B%20%5Bnative%20code%5D%20%7D';
  var es6string = 'function%20javaEnabled%28%29%20%7B%0A%20%20%20%20%5Bnative%20code%5D%0A%7D';
 
  if (window.devicePixelRatio) //If WebKit browser
  {
    var s = escape(navigator.javaEnabled.toString());
    if (s === v8string) {
      //' V099787 detected
    } else if (s === es6string) {
      //' ES6 detected 
    } else {
      //' JSC detected
    }
  } else {
    display("Not a WebKit browser");
  }
 
  function display(msg) {
    var p = document.createElement('p');
    p.innerHTML = msg;
    document.body.appendChild(p);
  }
 
})()

function check_ES6_1() {
    "use strict";
    try { eval("var foo = (x)=>x+1"); }
    catch (e) { return false; }
    return true;
}
function check_ES6_2() {
    "use strict";
    if (typeof Symbol == "undefined") return false;
    try {
        eval("class Foo {}");
        eval("var bar = (x) => x+1");
    } catch (e) { return false; }
    return true;
}
function isES6(){
    try{
        Function("() => {};"); return true;
    }catch(exception){
        return false;
    }
}