--- /dev/null
+var eq = require('../eq');
+
+/** Used for built-in method references. */
+var objectProto = global.Object.prototype;
+
+/** Used to check objects for own properties. */
+var hasOwnProperty = objectProto.hasOwnProperty;
+
+/**
+ * Assigns `value` to `key` of `object` if the existing value is not equivalent
+ * using [`SameValueZero`](http://ecma-international.org/ecma-262/6.0/#sec-samevaluezero)
+ * for equality comparisons.
+ *
+ * @private
+ * @param {Object} object The object to modify.
+ * @param {string} key The key of the property to assign.
+ * @param {*} value The value to assign.
+ */
+function assignValue(object, key, value) {
+ var objValue = object[key];
+ if ((!eq(objValue, value) ||
+ (eq(objValue, objectProto[key]) && !hasOwnProperty.call(object, key))) ||
+ (value === undefined && !(key in object))) {
+ object[key] = value;
+ }
+}
+
+module.exports = assignValue;