How to Implement Debounce and Throttle from Scratch

Identify that Debounce delays execution until a period of inactivity passes (e.g., search type-ahead), while Throttle guarantees execution at regular intervals during a continuous event (e.g., window scrolling).

Create a wrapper function that takes a callback function and a delay time as arguments. It must return a new inner function that preserves access to the outer variables via closures.

Declare a 'timeoutId' variable in the lexical scope of the parent wrapper function. This variable persists across multiple executions of the returned inner function.

Inside the returned function, immediately call 'clearTimeout(timeoutId)'. This clears any previously scheduled execution if the user triggers the event again before the delay completes.

Reset the 'timeoutId' with a new 'setTimeout'. Inside the timeout callback, invoke the original function using '.apply(this, arguments)' to perfectly maintain the execution context and forward passing arguments.

Create a wrapper function for throttle that accepts a function and a limit interval. Return a new inner function to handle incoming events.

Declare a boolean flag like 'isThrottling' in the parent lexical scope, initialized to false. This acts as a lock mechanism to ignore rapid successive calls.

Inside the returned function, check if 'isThrottling' is true. If it is, return immediately or save the last call parameters depending on whether trailing execution is required.

If 'isThrottling' is false, execute the callback using '.apply(this, arguments)' immediately. Switch 'isThrottling' to true to prevent any other executions.

Set a 'setTimeout' for the specified limit duration. When the timer finishes, flip 'isThrottling' back to false, allowing the next natural event to pass through the wrapper.