Bump to v4.0.0.

isNumber.js

@@ -0,0 +1,45 @@
+import isObjectLike from './isObjectLike';
+
+/** `Object#toString` result references. */
+var numberTag = '[object Number]';
+
+/** Used for built-in method references. */
+var objectProto = Object.prototype;
+
+/**
+ * Used to resolve the [`toStringTag`](http://ecma-international.org/ecma-262/6.0/#sec-object.prototype.tostring)
+ * of values.
+ */
+var objectToString = objectProto.toString;
+
+/**
+ * Checks if `value` is classified as a `Number` primitive or object.
+ *
+ * **Note:** To exclude `Infinity`, `-Infinity`, and `NaN`, which are classified
+ * as numbers, use the `_.isFinite` method.
+ *
+ * @static
+ * @memberOf _
+ * @category Lang
+ * @param {*} value The value to check.
+ * @returns {boolean} Returns `true` if `value` is correctly classified, else `false`.
+ * @example
+ *
+ * _.isNumber(3);
+ * // => true
+ *
+ * _.isNumber(Number.MIN_VALUE);
+ * // => true
+ *
+ * _.isNumber(Infinity);
+ * // => true
+ *
+ * _.isNumber('3');
+ * // => false
+ */
+function isNumber(value) {
+  return typeof value == 'number' ||
+    (isObjectLike(value) && objectToString.call(value) == numberTag);
+}
+
+export default isNumber;