kangax/es5-compat-table — Issue #12: Consider adding an ES5 identifier test
Author: mathiasbynens
Created: 2012-02-23 09:02:05+00:00
State: open

E.g. `var a\u200c\u200d` is a [valid identifier](http://mathiasbynens.be/notes/javascript-identifiers) as per ES5, but not all browsers/engines support it (yet).

This can easily be tested as follows:

```js
var browserWarning = (function() {
try {
Function('var a\u200c\u200d');
return true;
} catch(e) { }
}());
```

`browserWarning` will be true if ZWJ and ZWNJ characters are supported in `IdentifierPart`, else `undefined` (which is falsy).