Implement setInterval with setTimeout

setInterval vs setTimeout

• setTimeout: sets a timer which executes a function or specified piece of code once the timer expires.
• setInterval: repeatedly calls a function or executes a code snippet, with a fixed time delay between each call

setInterval can be implemented as recurisve setTimeout calls.

setInterval implementation with setTimeout

with signature

function _setInterval(fn: Function, delay: number): number;

The call stack will be:

— delay → fn() — delay → fn() — delay → fn() …

To delay the execution of fn, we could simply use setTimeout. Therefore, we create a wrapper function which encapsulates the logic which executes the original function.

function _setInterval(fn, delay) {
  // wrap the original function, recursively call the wrapper function with setTimeout 
  const wrapper = () => {
    fn();
    return setTimeout(wrapper, delay)
  }
  setTimeout(wrapper, delay);
}
_setInterval(console.log.bind(null, 'hello world'), 1000);

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