通用解决方案无需配置，自动检测所有输入修改，包括可满足的元素:

"use strict";
(() => {
const modified_inputs = new Set;
const defaultValue = "defaultValue";
// store default values
addEventListener("beforeinput", (evt) => {
    const target = evt.target;
    if (!(defaultValue in target || defaultValue in target.dataset)) {
        target.dataset[defaultValue] = ("" + (target.value || target.textContent)).trim();
    }
});
// detect input modifications
addEventListener("input", (evt) => {
    const target = evt.target;
    let original;
    if (defaultValue in target) {
        original = target[defaultValue];
    } else {
        original = target.dataset[defaultValue];
    }
    if (original !== ("" + (target.value || target.textContent)).trim()) {
        if (!modified_inputs.has(target)) {
            modified_inputs.add(target);
        }
    } else if (modified_inputs.has(target)) {
        modified_inputs.delete(target);
    }
});
// clear modified inputs upon form submission
addEventListener("submit", (evt) => {
    modified_inputs.clear();
    // to prevent the warning from happening, it is advisable
    // that you clear your form controls back to their default
    // state with evt.target.reset() or form.reset() after submission
});
// warn before closing if any inputs are modified
addEventListener("beforeunload", (evt) => {
    if (modified_inputs.size) {
        const unsaved_changes_warning = "Changes you made may not be saved.";
        evt.returnValue = unsaved_changes_warning;
        return unsaved_changes_warning;
    }
});
})();

您可以使用serialize()通过序列化表单值来创建URL编码的文本字符串，并检查表单在卸载前是否已更改

$(document).ready(function(){
    var form = $('#some-form'),
        original = form.serialize()

    form.submit(function(){
        window.onbeforeunload = null
    })

    window.onbeforeunload = function(){
        if (form.serialize() != original)
            return 'Are you sure you want to leave?'
    }
})

参考这个链接https://coderwall.com/p/gny70a/alert-when-leaving-page-with-unsaved-form 作者:弗拉基米尔·西多伦科

通过jquery

$('#form').data('serialize',$('#form').serialize()); // On load save form current state

$(window).bind('beforeunload', function(e){
    if($('#form').serialize()!=$('#form').data('serialize'))return true;
    else e=null; // i.e; if form state change show warning box, else don't show it.
});

你可以谷歌JQuery表单序列化函数，这将收集所有表单输入并保存在数组中。我想这个解释就足够了:)

var unsaved = false;
$(":input").change(function () {         
    unsaved = true;
});

function unloadPage() {         
    if (unsaved) {             
        alert("You have unsaved changes on this page. Do you want to leave this page and discard your changes or stay on this page?");
    }
} 
window.onbeforeunload = unloadPage;

根据之前的回答，并从堆栈溢出的不同地方拼凑在一起，这里是我提出的解决方案，当你实际上想要提交你的更改时，它可以处理这种情况:

window.thisPage = window.thisPage || {};
window.thisPage.isDirty = false;

window.thisPage.closeEditorWarning = function (event) {
    if (window.thisPage.isDirty)
        return 'It looks like you have been editing something' +
               ' - if you leave before saving, then your changes will be lost.'
    else
        return undefined;
};

$("form").on('keyup', 'textarea', // You can use input[type=text] here as well.
             function () { 
                 window.thisPage.isDirty = true; 
             });

$("form").submit(function () {
    QC.thisPage.isDirty = false;
});
window.onbeforeunload = window.thisPage.closeEditorWarning;

值得注意的是，IE11似乎要求closeEditorWarning函数返回undefined才能不显示警报。

Eerik Sven Puudist的解决方案…

var isSubmitting = false;

$(document).ready(function () {
    $('form').submit(function(){
        isSubmitting = true
    })

    $('form').data('initial-state', $('form').serialize());

    $(window).on('beforeunload', function() {
        if (!isSubmitting && $('form').serialize() != $('form').data('initial-state')){
            return 'You have unsaved changes which will not be saved.'
        }
    });
})

…在复杂的面向对象设置中，自发地为我完成了这项工作，而不需要任何更改。

我应用的唯一更改是引用具体的表单(每个文件只有一个表单)，称为“formForm”('form' -> '#formForm'):

<form ... id="formForm" name="formForm" ...>

特别出色的是，提交按钮被“单独保留”了。

此外，它也适用于最新版本的Firefox(截至2019年2月7日)。