Javascript timer already run before click start

Question

Halo, i have function timer, but the timer is already run before i click start. how to solve it, i want when i click start, the timer will be running. if i deleted seconds++ in first function, the time not running even i click start button the time is still 0. Thank you for help. this is my code

var h1 = document.getElementsByTagName('h1')[0],
    start = document.getElementById('start'),
    stop = document.getElementById('stop'),
    seconds = 0, minutes = 0, hours = 0,
    t;

function add() {
    seconds++;
    if (seconds >= 60) {
        seconds = 0;
        minutes++;
        if (minutes >= 60) {
            minutes = 0;
            hours++;
        }
    }
    
    h1.textContent = (hours ? (hours > 9 ? hours : "0" + hours) : "00") + ":" + (minutes ? (minutes > 9 ? minutes : "0" + minutes) : "00") + ":" + (seconds > 9 ? seconds : "0" + seconds);

    timer();
}
function timer() {
    t = setTimeout(add, 1000);
}
timer();


/* Start button */
start.onclick = timer;

/* Stop button */
stop.onclick = function() {
    clearTimeout(t);
}

<h1><time>00:00:00</time></h1>
<button id="start">start</button>
<button id="stop">stop</button>

Answer 1

Remove timer(); from your code

function timer() {
    t = setTimeout(add, 1000);
}
//timer();


/* Start button */
start.onclick = timer;