Javascript函数仅在禁用其他javascript函数时才起作用[重复]答案

【问题标题】：Javascript functions only work when the other javascript functions are disabled [duplicate]Javascript函数仅在禁用其他javascript函数时才起作用[重复]
【发布时间】：2019-09-20 18:30:15
【问题描述】：

我制作了一个测试网站，用于试验 javascript。

我创建的所有 3 个函数都独立工作，但只有在其他函数被禁用时（当它们是 cmets 时）。如果我不评论其他功能，所有功能都会表现得很奇怪并且无法正常工作（主题转换器不记得主题，页面加载时 TopButton 会显示在顶部等）。

//HTML

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <title>K E K</title>
    <link rel="stylesheet" type="text/css" href="style.css">
    <script type="text/javascript" src="exde.js"></script>
</head>
<body>
    <button onclick="ChangeTheme()">Change Theme</button>
    <button onclick="ChangeTopButton()">Change Top-Button</button>
    <button onclick="ToggleTopButton()">Toggle Top-Button</button>
    <button id="topbutton" onclick="TopButton()">Go Top</button>

    <h1>Lorem Ipsum</h1>
    <p>Lorem ipsum dolor sit amet, ...</p>
</body>
</html>

//CSS
body {
    background-color: #CFF;
}
button#topbutton {
    position: fixed;
}
.displaynone {
    display: none;
}

//JS

// Change Theme
window.onload = function LoadTheme() {
    if (localStorage.theme) {
        if (localStorage.theme == "dark") {
            SetThemeDark();
        }
    }
    else {
        localStorage.setItem("theme","light");
    }
}
function ChangeTheme() {
    if (localStorage.theme == "dark") {
        SetThemeLight();
        localStorage.theme = "light";
    }
    else {
        SetThemeDark();
        localStorage.theme = "dark";
    }
}
function SetThemeDark() {
    let a = document.getElementsByTagName('body')[0];
    a.style.backgroundColor = '#444';
}
function SetThemeLight() {
    let a = document.getElementsByTagName('body')[0];
    a.style.backgroundColor = '#CFF';
}

// Change Top Button
window.onload = function LoadTopButton() {
    if (localStorage.topbutton) {
        switch(localStorage.topbutton) {
            case "bottomright":
                SetBottomRight();
                break;
            case "bottomleft":
                SetBottomLeft();
                break;
            case "topleft":
                SetTopLeft();
                break;
            case "topright":
                SetTopRight();
                break;
            default:
                SetBottomRight();
        }
    }
    else {
        localStorage.setItem("topbutton","bottomright");
        SetBottomRight();
    }
}
function ChangeTopButton() {
    switch(localStorage.topbutton) {
        case "bottomright":
            SetBottomLeft();
            localStorage.topbutton = "bottomleft";
            break;
        case "bottomleft":
            SetTopLeft();
            localStorage.topbutton = "topleft";
            break;
        case "topleft":
            SetTopRight();
            localStorage.topbutton = "topright";
            break;
        case "topright":
            SetBottomRight();
            localStorage.topbutton = "bottomright";
            break;
        default:
            SetBottomRight();
            localStorage.topbutton = "bottomright";
    }
}
function TopButton() {
    document.documentElement.scrollTop = 0;
}
function SetBottomLeft() {
    let a = document.getElementById("topbutton");
    a.style.right = "auto";
    a.style.top = "auto";
    a.style.left = "5px";
    a.style.bottom = "5px";
}
function SetBottomRight() {
    let a = document.getElementById("topbutton");
    a.style.left = "auto";
    a.style.top = "auto";
    a.style.right = "5px";
    a.style.bottom = "5px";
}
function SetTopLeft() {
    let a = document.getElementById("topbutton");
    a.style.right = "auto";
    a.style.bottom = "auto";
    a.style.left = "5px";
    a.style.top = "5px";
}
function SetTopRight() {
    let a = document.getElementById("topbutton");
    a.style.left = "auto";
    a.style.bottom = "auto";
    a.style.right = "5px";
    a.style.top = "5px";
}

// Toggle Top Button
window.onload = function LoadTopButtonOnLoad() {
    if (localStorage.displayButton) {
        if (localStorage.displayButton == "no") {
            DeleteTopButton();
        }
    }
    else {
        localStorage.setItem("displayButton","yes");
    }
}
function ToggleTopButton() {
    if (localStorage.displayButton == "yes") {
        DeleteTopButton();
        localStorage.displayButton = "no";
    }
    else {
        ShowTopButton();
        localStorage.displayButton = "yes";
    }
}
function DeleteTopButton() {
    let a = document.getElementById("topbutton");
    a.classList.add("displaynone");
}
function ShowTopButton() {
    let a = document.getElementById("topbutton");
    a.classList.remove("displaynone");
}

【问题讨论】：

如果你不想为同一个事件向同一个对象添加多个监听器，请使用.addEventListener
或者将函数声明为单独的命名函数并在window.onload中调用它们，例如`window.onload = function () { LoadTheme();加载顶部按钮（）； LoadTopButtonOnLoad(); }
它现在可以与 window.addEventListener 一起使用。

标签： javascript html

【解决方案1】：

原因是你用另一个函数覆盖了 onload。

window.onload = 1;
window.onload = 2; // 1 will not work anymore

改用 .addEventListener。

window.addEventListener('load', function() {
});

// instead of 
window.load = function () {
}

【讨论】：