High JavaScript Question 189 of 229

How would you implement throttle with leading and trailing edges for scroll?

Frontend Master · Speak this in 60–90 seconds · Faridabad & Delhi NCR

IdeaJavaScript

HowWhat happens inside

Why they askShows real use

Leading runs immediately, then ignores calls until the window ends

Why interviewers care about JavaScript:

This is a process

question about JavaScript.

Panels listen for order,

trade-offs, and what you would actually do on a Frontend project - not buzzwords.

Stay structured

Name the idea, why it exists, then one short example.

Close cleanly

End with when you use it and one common pitfall.

Before you speak the answer, walk the interviewer through these steps:

1
Leading runs immediately, then
ignores calls until the window ends
2
trailing fires once more
with the last args if calls happened during the wait.
3
Scroll position UIs usually
want both so the first frame updates and the last position is not dropped.
4
I store lastArgs and
a timeout, which is what I sketch on a board.
5
Common mistake
What juniors usually get wrong.
6
Close
When you pick this over the alternative.

Here's a short line you can speak, broken into clear beats:

Say this line

“Scroll position UIs usually want both so the first frame updates and the last po”

Break into beats

ScrollpositionUIsusuallywantboth

Speaking order

2987408337471632900

Note: Adapt this scaffold to your own project — keep it under 60–90 seconds.

Leading runs immediately, then ignores calls until the window ends trailing fires once more with the last args if calls happened during the wait.