modernizr/feature-detects/es5/syntax.js

Modernizr is a JavaScript library that detects HTML5 and CSS3 features in the user’s browser.

/*!
{
  "name": "ES5 Syntax",
  "property": "es5syntax",
  "notes": [{
    "name": "ECMAScript 5.1 Language Specification",
    "href": "http://www.ecma-international.org/ecma-262/5.1/"
  }, {
    "name": "original implementation of detect code",
    "href": "http://kangax.github.io/es5-compat-table/"
  }],
  "authors": ["Ron Waldon (@jokeyrhyme)"],
  "warnings": ["This detect uses `eval()`, so CSP may be a problem."],
  "tags": ["es5"]
}
!*/
/* DOC
Check if browser accepts ECMAScript 5 syntax.
*/
define(['Modernizr'], function(Modernizr) {
  Modernizr.addTest('es5syntax', function() {
    var value, obj, stringAccess, getter, setter, reservedWords, zeroWidthChars;
    try {
      /* eslint no-eval: "off" */
      // Property access on strings
      stringAccess = eval('"foobar"[3] === "b"');
      // Getter in property initializer
      getter = eval('({ get x(){ return 1 } }).x === 1');
      eval('({ set x(v){ value = v; } }).x = 1');
      // Setter in property initializer
      setter = value === 1;
      // Reserved words as property names
      eval('obj = ({ if: 1 })');
      reservedWords = obj['if'] === 1;
      // Zero-width characters in identifiers
      zeroWidthChars = eval('_\u200c\u200d = true');

      return stringAccess && getter && setter && reservedWords && zeroWidthChars;
    } catch (ignore) {
      return false;
    }
  });
});