code: function assocIndexOf(array, key) {
    var length = array.length;
    while (length--) {
      if (eq_1(array[length][0], key)) {
        return length;
      }
    }
    return -1;
  }
docs: Gets the index at which the `key` is found in `array` of key-value pairs.
  
  @private
  @param {Array} array The array to inspect.
  @param {*} key The key to search for.
  @returns {number} Returns the index of the matched value, else `-1`.