function assocIndexOf(array, key) {
	  var length = array.length;
	  while (length--) {
	    if (eq(array[length][0], key)) {
	      return length;
	    }
	  }
	  return -1;
	}
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`.