TypeScript implementation of debounce and throttle function

Debounce creates a new function g, which when called will delay the invocation of the original function f until n milliseconds, BUT drop previous pending delayed emissions if a new invocation is made before n milliseconds.

It's very useful for scenarios when it's better to limit the number of times the function is called. E.g. think of search input which fetches data from API. It's enough display search results after user has stopped entering characters for some time.

Install

npm i p-debounce-throttle -S

Function arguments

1import { debounce } from "ts-debounce";
2
3const debouncedFunction = debounce(originalFunction, waitMilliseconds, options);

• originalFunction
  • the function which we want to debounce
• waitMilliseconds
  • how many seconds must pass after most recent function call, for the original function to be called
• options
  • isImmediate (boolean)
    • if set to true then originalFunction will be called immediately, but on subsequent calls of the debounced function original function won't be called, unless waitMilliseconds passed after last call
  • maxWait (number)
    • if defined it will call the originalFunction after maxWait time has passed, even if the debounced function is called in the meantime
      • e.g. if wait is set to 100 and maxWait to 200, then if the debounced function is called every 50ms, then the original function will be called after 200ms anyway
  • callback (function)
    • it is called when originalFunction is debounced and receives as first parameter returned data from originalFunction

Cancellation

The returned debounced function can be cancelled by calling cancel() on it.

1const debouncedFunction = debounce(originalFunction, waitMilliseconds, options);
2
3debouncedFunction.cancel();

Promises

ts-debounce-throttle has Promise support. Everytime you call debounced function a promise is returned which will be resolved when the original function will be finally called. This promise will be rejected, if the debounced function will be cancelled.

You can also debounce a function f which returns a promise. The returned promise(s) will resolve (unless cancelled) with the return value of the original function.

1const asyncFunction = async () => "value";
2const g = debounce(asyncFunction);
3const returnValue = await g();
4returnValue === "value"; // true

Credits & inspiration

This implementation is based upon following sources:

• JavaScript Debounce Function by David Walsh
• Lodash implementation
• p-debounce