Coding Challenge Practice - Question 112

The task is to implement setInterval.

the boilerplate code

function mySetInterval(func, delay, period) {
  // your code here
}

/**
 * @param { number } id
 */
function myClearInterval(id) {

}

Create the global states

let nextId = 1;
const intervals = new Map()

nextId simulates browser-generated interval IDs and intervals keep track of active intervals.

Create a progressive interval

func mySetInterval(func, delay, period) {

Create an ID

const id = nextId++;

It ensures every interval has a unique identifier.

Create an interval state

const state = {
  active: true,
  count: 0,
  timeoutId: null
}

active stops future executions when cleared. count is the number of times the function has been run. timeoutId is the current setTimeout reference.

Each period after every time the function runs is determined by

const waitTime = delay + period * state.count;

Execute and reschedule

state.timeoutId = setTimeout(() => {
  if (!state.active) return;

  func();
  state.count++;
  schedule();
}, waitTime);

Start the first timer

schedule();
intervals.set(id, state);

Return ID

return id;

To clear the interval after it runs

function myClearInterval(id) {

If the interval doesn't exist, do nothing

const state = intervals.get(id);
if (!state) return;

Stop future executions

state.active = false;

Cancel pending timeout

clearTimeout(state.timeoutId);

Remove the interval from tracking

intervals.delete(id);

The final code

let nextId = 1;
const intervals = new Map();
function mySetInterval(func, delay, period) {
  // your code here
  const id = nextId++;

  const state = {
    active: true,
    count: 0,
    timeoutId: null
  }

  function schedule() {
    const waitTime = delay + period * state.count;

    state.timeoutId = setTimeout(() => {
      if(!state.active) return;

      func();
      state.count++;
      schedule();
    }, waitTime)
  }

  schedule();
  intervals.set(id, state);

  return id;
}


function myClearInterval(id) {
  const state = intervals.get(id);
  if(!state) return;

  state.active = false;
  clearTimeout(state.timeoutId);
  intervals.delete(id)
}

That's all folks!