Function filter

test/babel.js:2131–2138

(xs, f)

	};

	function filter(xs, f) {
	  if (xs.filter) return xs.filter(f);
	  var res = [];
	  for (var i = 0; i < xs.length; i++) {
	    if (f(xs[i], i, xs)) res.push(xs[i]);
	  }
	  return res;
	}

	// String.prototype.substr - negative index don't work in IE8
	var substr = 'ab'.substr(-1) === 'b' ? function (str, start, len) {