Debouncing is a technique used to control how many times we allow a function to be executed over time. When a JavaScript function is debounced with a wait time of X milliseconds, it must wait until after X milliseconds have elapsed since the debounced function was last called.

You almost certainly have encountered debouncing in your daily lives before (e.g. when entering an elevator). Only after X duration of not pressing the "Door open" button (the debounced function not being called) will the elevator door actually close (the callback function is executed).

Implement a debounce function which accepts a callback function and a wait duration. Calling debounce() returns a function which has debounced invocations of the callback function following the behavior described above.

Examples

let i = 0;
function increment() {
  i++;
}
const debouncedIncrement = debounce(increment, 100);

// t = 0: Call debouncedIncrement().
debouncedIncrement(); // i = 0

// t = 50: i is still 0 because 100ms have not passed.

// t = 100: increment() was invoked and i is now 1.

debouncedIncrement() is called multiple times.

let i = 0;
function increment() {
  i++;
}
const debouncedIncrement = debounce(increment, 100);
// t = 0: Call debouncedIncrement().
debouncedIncrement(); // i = 0
// t = 50: i is still 0 because 100ms have not passed.
//  Call debouncedIncrement() again.
debouncedIncrement(); // i = 0
// t = 100: i is still 0 because it has only
//  been 50ms since the last debouncedIncrement() at t = 50.
// t = 150: Because 100ms have passed since
//  the last debouncedIncrement() at t = 50,
//  increment was invoked and i is now 1 .

Follow up

• Debounce with a cancel() method to cancel delayed invocations and a flush() method to immediately invoke them.
• Implement throttle, which is similar to debounce but a little different.

Reading

• Debounce on Lodash Documentation

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