Bump to v4.0.0.

toString.js

@@ -0,0 +1,46 @@
+import _Symbol from './internal/_Symbol';
+import isSymbol from './isSymbol';
+
+/** Used as references for various `Number` constants. */
+var INFINITY = 1 / 0;
+
+/** Used to convert symbols to primitives and strings. */
+var symbolProto = _Symbol ? _Symbol.prototype : undefined,
+    symbolToString = _Symbol ? symbolProto.toString : undefined;
+
+/**
+ * Converts `value` to a string if it's not one. An empty string is returned
+ * for `null` and `undefined` values. The sign of `-0` is preserved.
+ *
+ * @static
+ * @memberOf _
+ * @category Lang
+ * @param {*} value The value to process.
+ * @returns {string} Returns the string.
+ * @example
+ *
+ * _.toString(null);
+ * // => ''
+ *
+ * _.toString(-0);
+ * // => '-0'
+ *
+ * _.toString([1, 2, 3]);
+ * // => '1,2,3'
+ */
+function toString(value) {
+  // Exit early for strings to avoid a performance hit in some environments.
+  if (typeof value == 'string') {
+    return value;
+  }
+  if (value == null) {
+    return '';
+  }
+  if (isSymbol(value)) {
+    return _Symbol ? symbolToString.call(value) : '';
+  }
+  var result = (value + '');
+  return (result == '0' && (1 / value) == -INFINITY) ? '-0' : result;
+}
+
+export default toString;