es6-feature-detection.js

var str = 'class ಠ_ಠ extends Array {constructor(j = "a", ...c) {const q = (({u: e}) => {return { [`s${c}`]: Symbol(j) };})({});super(j, q, ...c);}}' + 
          'new Promise((f) => {const a = function* (){return "\u{20BB7}".match(/./u)[0].length === 2 || true;};for (let vre of a()) {' +
          'const [uw, as, he, re] = [new Set(), new WeakSet(), new Map(), new WeakMap()];break;}f(new Proxy({}, {get: (han, h) => h in han ? han[h] ' + 
          ': "42".repeat(0o10)}));}).then(bi => new ಠ_ಠ(bi.rd));';

try {
  eval(str);
} catch(e) {
  alert('Your browser does not support ES6!')
}

/* 
 * All credits to Netflix for providing this approach to ES6 feature detection. Although this could be written in many different ways
 * this proved to be the most direct and elegant approach for me.
 * License: MIT
*/

Found an issue. Need to replace

\u{20BB7}

With

\\u{20BB7}

Otherwise that is parsed outside of the eval and it will cause failures with things like UglifyJS that expects ES5

It also rises a parse error in IE 11 Expected hexadecimal digit, and thus fails its purpose.