node.js - executing setTimeout function before the time if socket has received some request -

i have use case executing settimeout function after 20 seconds want function executed if socket connection front end has returned before 20 seconds. , don't want run after 20 seconds in case. how can achieve this.

the simplest scheme here put code in function use settimeout() and, if timer still running, cancel timer , call function directly:

function dosometask() {     // code here task }  // schedule task run in 20 seconds // remember timer handle know it's running let timer = settimeout(() => {     timer = null;     dosometask(); }, 20*1000);  // elsewhere in code want call function // earlier timer (if hasn't been called) if (timer) {     cleartimeout(timer);     timer = null;     dosometask(); } 

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promises can offer benefit here because make sure given promise ever resolved or rejected once , can taken advantage of here. use them elegantly, i'd create little state object makes simple use.

function delayexecute(fn, t) {     let obj = {state: "timer"};     let p = new promise((resolve, reject) => {         obj.runnow = resolve;         obj.cancel = reject;         settimeout(resolve, t);     }).catch(err => {         obj.state = "err";         throw err;     }).then(() => {         fn();         obj.state = "done";     });     return obj; }  function dosometask() {     // code here task }  let task = delayexecute(dosometask, 20*1000);  // time later, run sooner (if hasn't run) // calling .runnow() method after function has run nothing task.runnow(); 

this same interface built without promises too. thought i'd show how leverage of one-way state transitions of promises purpose.