How can I run a function after a user has stopped typing in an Input field?

Question

In a current project I`m making, I have a timer which accepts values in format "00:00:00" or "hours:minutes:seconds" in an input field and a button which converts the formats to "00:00:00" if neccessery, and starts incrementing the time on the timer. I want to make it so a "CheckInput()" function runs as soon as the user stops typing in the input field before he even presses the start button. I want this to be pure JavaScript without frameworks if possible.

"OnMouse" events will not work in this case, I thought about checking for "onkeydown" events between an interval of about 0,2-0,5 s and if there are none to assume the user has stopped typing, but can`t seem to figure out how to implement it correctly.

Answer 1

Vanilla js solution, assuming the stopping time is 2 seconds

//setup before functions
let typingTimer;                //timer identifier
let doneTypingInterval = 2000;  //time in ms (2 seconds)
let myInput = document.getElementById('myInput');

//on keyup, start the countdown
myInput.addEventListener('keyup', () => {
    clearTimeout(typingTimer);
    if (myInput.value) {
        typingTimer = setTimeout(doneTyping, doneTypingInterval);
    }
});

//user is "finished typing," do something
function doneTyping () {
    //do something
}