--- /dev/null
+var eq = require('./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;
+}
+
+module.exports = assocIndexOf;