--- /dev/null
+/**
+ * Checks if `value` is suitable for use as unique object key.
+ *
+ * @private
+ * @param {*} value The value to check.
+ * @returns {boolean} Returns `true` if `value` is suitable, else `false`.
+ */
+function isKeyable(value) {
+ var type = typeof value;
+ return type == 'number' || type == 'boolean' ||
+ (type == 'string' && value !== '__proto__') || value == null;
+}
+
+module.exports = isKeyable;