const startBtn = document.querySelector('.startBtn');
const pauseBtn = document.querySelector('.pauseBtn');
const ResetBtn = document.querySelector('.resetBtn');
const time = document.querySelector('.time');

let seconds = 0;
let secondsStr = '00';
let minutes = 0;
let minutesStr = '00';
let hours = 0;
let hoursStr = '00';
let timeText = `${hoursStr}:${minutesStr}:${secondsStr}`;
time.textContent = timeText;

function addSecond() {
    seconds++;
    secondsStr = seconds.toString();
    if (seconds < 10) {
        secondsStr = `0${secondsStr}`;
    }
    
    if(seconds >= 60) {
        seconds = 0;
        minutes++;
        minutesStr = minutes.toString();
        if (minutes < 10) {
            minutesStr = `0${minutesStr}`;
        }
        
        if(minutes >= 60) {
            minutes = 0;
            hours++;
            hoursStr = hours.toString();
            if (hours < 10) {
                hoursStr = `0${hoursStr}`;
            }
        }
    }
    timeText = `${hoursStr}:${minutesStr}:${secondsStr}`;
    time.textContent = timeText;
}

startBtn.addEventListener('click', startWatch);
pauseBtn.addEventListener('click', pauseWatch);

function startWatch() {
    const startTimer = setInterval(addSecond, 1000);
}

function pauseWatch() {
    clearInterval(startTimer);
}

<div class="stopwatch">
        <div class="time"></div>
        <div class="stopwatchBtns">
            <button class="startBtn stopwatchBtn">Start</button>
            <button class="pauseBtn stopwatchBtn">Pause</button>
            <button class="resetBtn stopwatchBtn">Reset</button>
        </div>
    </div>

基本上，当调用pauseWatch函数时，我希望它清除startTimer间隔，但它说它没有定义，即使它不确定它是否与变量范围有关，但即使它是，我也不知道如何修复它
我尝试重新安排一些代码，但似乎没有任何帮助