--- /dev/null
+/*!
+ * is-number <https://github.com/jonschlinkert/is-number>
+ *
+ * Copyright (c) 2014-2015, Jon Schlinkert.
+ * Licensed under the MIT License.
+ */
+
+'use strict';
+
+var typeOf = require('kind-of');
+
+module.exports = function isNumber(num) {
+ var type = typeOf(num);
+ if (type !== 'number' && type !== 'string') {
+ return false;
+ }
+ var n = +num;
+ return (n - n + 1) >= 0 && num !== '';
+};