建在Wasim A的顶部。使用序列化的好主意。这里的问题是，在提交表单时也显示了警告。这里已经修好了。

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.'
        }
    });
})

它已经在Chrome和IE 11上进行了测试。

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;

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:)

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。

你可以在这里查看详细的解释: http://techinvestigations.redexp.in/comparison-of-form-values-on-load-and-before-close/

主要代码:

function formCompare(defaultValues, valuesOnClose) {
 
    // Create arrays of property names
    var aPropsFormLoad = Object.keys(defaultValues);
    var aPropsFormClose = Object.keys(valuesOnClose);
 
    // If number of properties is different,
    // objects are not equivalent
    if (aPropsFormLoad.length != aPropsFormClose.length) {
        return false;
    }
 
    for (var i = 0; i < aPropsFormLoad.length; i++) {
        var propName = aPropsFormLoad[i];
 
        // If values of same property are not equal,
        // objects are not equivalent
        if (defaultValues[aPropsFormLoad]+"" !== valuesOnClose[aPropsFormLoad]+"") {
            return false;
        }
    }
 
    // If we made it this far, objects
    // are considered equivalent
    return true;
 
}

//add polyfill for older browsers, as explained on the link above

//use the block below on load
    for(i=0; i < document.forms[0].elements.length; i++){
    console.log("The field name is: " + document.forms[0].elements[i].name +
        " and it’s value is: " + document.forms[0].elements[i].value );
    aPropsFormLoad[i] = document.forms[0].elements[i].value;
    }

//create a similar array on window unload event.

//and call the utility function
    if (!formCompare(aPropsOnLoad, aPropsOnClose))
    {
    //perform action: 
    //ask user for confirmation or
    //display message about changes made
    }

简短的回答:

let pageModified = true

window.addEventListener("beforeunload", 
  () => pageModified ? 'Close page without saving data?' : null
)