The use case here, copied from my JSDoc block:
Example: Given array `sites`, which needs to be updated on keypress, the user types "abc". The net request for "abc" fires, but takes 5sec to return. Within that 5sec, the user added "d" to the input, and a new net request was fired which returned immediately. Our data array will now contain the results from the "abc" input rather than the "abcd" input as the user expects.