javascript - 无法读取 null 的属性 'parentNode'。我在控制台中遇到错误

Question

 var button1 = document.getElementById("start");
var button2 = document.getElementById("stop");
var timegraph = document.getElementById("ceas");
var lapButton = document.getElementById("lap");
var lame = document.getElementById("test");
var time = 0;
var ResetStart = 0;
var myInterval;
var body = document.getElementById("body");
var action = document.getElementById("lappara");
function Start() {
    if (ResetStart == 0) {
        ResetStart = 1;
        Running();
        button1.innerHTML = "Pause";
    }
    else {
        ResetStart = 0;
        button1.innerHTML = "Resume";
        clearInterval(myInterval);
    }
}
function Reset() {
    time = 0;
    ResetStart = 0;
    button1.innerHTML = "Start";
    timegraph.innerHTML = "00:00:00:00";
    clearInterval(myInterval);
    var aux = action.parentNode;
    aux.removeChild(action);
}
function OnGoing() {
    time++;
    var hours = Math.floor(time / 100 / 60 / 60);
    var minutes = Math.floor(time / 100 / 60 % 60);
    var seconds = Math.floor(time / 100 % 60);
    var hundreds = Math.floor(time / 10 % 10);
    var thousands = time % 10;
    if (hours < 10) {
        hours = "0" + hours;
    }
    if (minutes < 10) {
        minutes = "0" + minutes;
    }
    if (seconds < 10) {
        seconds = "0" + seconds;
    }
    timegraph.innerHTML = hours + ":" + minutes + ":" + seconds + ":" + hundreds + thousands;
}
function Running() {
    if (ResetStart == 1) {
        myInterval = setInterval(OnGoing, 10);
    }
    else {
        timegraph.innerHTML = "00:00:00:00";
    }
}
function Lap() {
    var n = document.createElement("p");
    n.setAttribute("id", "lappara");
    var text = document.createTextNode(timegraph.innerHTML);
    n.appendChild(text);
    body.insertBefore(n, action);
}

每当我调用 Reset() 函数时，我都会收到上述错误。这段代码应该是一个秒表，而 Lap() 函数只是创建圈数。我查找了一些解决方案，但似乎没有一个有效。如果可以的话请帮助我

Answer 1

我假设您可以调用一次Reset()，但下次调用它时会出现错误。这是因为 aux.removeChild(action)。您删除 action，然后尝试获取它的parentNode - 这就是问题所在。