Imagine you have a JavaScript function that makes a request to your server. Perhaps it is sending user input from a textarea to be processed by the server. You may want to wrap this function in a keyboard event listener so that you are sure to react immediately to any user input. However, as the user starts typing away into this text area you may find that way to many requests are being fired off to the server. The request needs to be throttled.

You can roll your own approach to sufficiently intermittent server calls. Though, it turns out that underscore.js comes with two functions out of the box for this kind of behavior.

• throttle will give you a function that wraps your function in a way that essentially rate-limits it to being called at most once every N milliseconds.

• debounce, on the other hand, will give you a function that only calls your function once N milliseconds has passed since it was last called.

These are two subtly different approaches to making sure a function gets called, just not too often.

h/t Jake Worth