Polish notation expression eval

gistfile1.js

var polish = (function () {
	var ops = ['*','/','+','-']
	.reduce( function(a, b){
		a[b] = Function ( 'x', 'return x[0]=x.shift()' + b + 'x[0], x' );
		return a;
	}, {});
	Object.getOwnPropertyNames(Math)
	.forEach( function(b){
		var l = Math[b].length, f = '';
		if (l === void 0) f = 'x.unshift(Math.' + b + '), x';
		else if (l === 0) f = 'x.unshift(Math.' + b + '()), x';
		else if (l === 1) f = 'x[0]=Math.' + b + '(x[0]), x';
		else if (l === 2) f = 'x[0]=Math.' + b + '(x.shift(),x[0]), x';
		ops[b] = Function ( 'x', 'return ' + f);
	});
	return function(s) {
		return s.split(/\s+/)
		.reduce( function (a, b) {
			if (ops[b]) ops[b](a);
			else if (!isNaN(b) && b!='') a.unshift(+b);
			return a;
		}, []);
	};
})();

// polish ("1 2 3 + + sin");

/* ES 6 basic
var polish = (function () {
  var ops = "+-/*".split("").reduce((a,b)=>(a[b]=Function("x","return x[0]=x.shift()"+b+"x[0],x"),a),{});
  return (s)=>s.split(/\s+/).reduce((a,b)=>(ops[b]?ops[b](a):!isNaN(b)&&b!=''?(a.unshift(+b),a):a),[]);
})();
polish("1 2 3 + +")
*/