Bump to v4.0.0.

internal/assocIndexOf.js

@@ -0,0 +1,22 @@
+import eq from '../eq';
+
+/**
+ * Gets the index at which the first occurrence of `key` is found in `array`
+ * of key-value pairs.
+ *
+ * @private
+ * @param {Array} array The array to search.
+ * @param {*} key The key to search for.
+ * @returns {number} Returns the index of the matched value, else `-1`.
+ */
+function assocIndexOf(array, key) {
+  var length = array.length;
+  while (length--) {
+    if (eq(array[length][0], key)) {
+      return length;
+    }
+  }
+  return -1;
+}
+
+export default assocIndexOf;