The result of debounce(f, ms) decorator should be a wrapper that passes the call to f at maximum once per ms milliseconds.

In other words, when we call a “debounced” function, it guarantees that all other future in the closest ms milliseconds will be ignored.

For instance:

let f = debounce(alert, 1000);

f(1); // runs immediately
f(2); // ignored

setTimeout( () => f(3), 100); // ignored ( only 100 ms passed )
setTimeout( () => f(4), 1100); // runs
setTimeout( () => f(5), 1500); // ignored (less than 1000 ms from the last run)

In practice debounce is useful for functions that retrieve/update something when we know that nothing new can be done in such a short period of time, so it’s better not to waste resources.

Open a sandbox with tests.

function debounce(f, ms) {

  let isCooldown = false;

  return function() {
    if (isCooldown) return;

    f.apply(this, arguments);

    isCooldown = true;

    setTimeout(() => isCooldown = false, ms);
  };

}