测试了伊莱·格雷的通用解决方案，只有在我把代码简化到

  'use strict';
  (() => {
    const modified_inputs = new Set();
    const defaultValue = 'defaultValue';
    // store default values
    addEventListener('beforeinput', evt => {
      const target = evt.target;
      if (!(defaultValue in target.dataset)) {
        target.dataset[defaultValue] = ('' + (target.value || target.textContent)).trim();
      }
    });

    // detect input modifications
    addEventListener('input', evt => {
      const target = evt.target;
      let original = target.dataset[defaultValue];

      let current = ('' + (target.value || target.textContent)).trim();

      if (original !== current) {
        if (!modified_inputs.has(target)) {
          modified_inputs.add(target);
        }
      } else if (modified_inputs.has(target)) {
        modified_inputs.delete(target);
      }
    });

    addEventListener(
      'saved',
      function(e) {
        modified_inputs.clear()
      },
      false
    );

    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;
      }
    });

  })();

对his的修改删除了target[defaultValue]的使用，只使用target。dataset[defaultValue]来存储真实的默认值。

我添加了一个'saved'事件监听器，'saved'事件将由您自己在保存操作成功时触发。

但是这个“通用”的解决方案只适用于浏览器，而不适用于应用程序的webview，例如微信浏览器。

为了使它在微信浏览器(部分)也工作，另一个改进再次:

  'use strict';
  (() => {
    const modified_inputs = new Set();
    const defaultValue = 'defaultValue';
    // store default values
    addEventListener('beforeinput', evt => {
      const target = evt.target;
      if (!(defaultValue in target.dataset)) {
        target.dataset[defaultValue] = ('' + (target.value || target.textContent)).trim();
      }
    });

    // detect input modifications
    addEventListener('input', evt => {
      const target = evt.target;
      let original = target.dataset[defaultValue];

      let current = ('' + (target.value || target.textContent)).trim();

      if (original !== current) {
        if (!modified_inputs.has(target)) {
          modified_inputs.add(target);
        }
      } else if (modified_inputs.has(target)) {
        modified_inputs.delete(target);
      }

      if(modified_inputs.size){
        const event = new Event('needSave')
        window.dispatchEvent(event);
      }
    });

    addEventListener(
      'saved',
      function(e) {
        modified_inputs.clear()
      },
      false
    );

    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;
      }
    });

    const ua = navigator.userAgent.toLowerCase();

    if(/MicroMessenger/i.test(ua)) {
      let pushed = false

      addEventListener('needSave', evt => {
        if(!pushed) {
          pushHistory();

          window.addEventListener("popstate", function(e) {
            if(modified_inputs.size) {
              var cfi = confirm('确定要离开当前页面嘛？' + JSON.stringify(e));
              if (cfi) {
                modified_inputs.clear()
                history.go(-1)
              }else{
                e.preventDefault();
                e.stopPropagation();
              }
            }
          }, false);
        }

        pushed = true
      });
    }

    function pushHistory() {
      var state = {
        title: document.title,
        url: "#flag"
      };
      window.history.pushState(state, document.title, "#flag");
    }
  })();

下面的一句话对我很管用。

window.onbeforeunload = s => modified ? "" : null;

根据应用程序的状态将modified设置为true或false。

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
    }

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。

我做了不同的，分享在这里，以便有人可以得到帮助，只测试Chrome。

我想警告用户关闭标签只有当有一些变化。

<input type="text" name="field" value="" class="onchange" />

var ischanged = false;

$('.onchange').change(function () {
    ischanged = true;
});

window.onbeforeunload = function (e) {
    if (ischanged) {
        return "Make sure to save all changes.";
    }        
};

工作很好，但有一个其他的问题，当我提交的形式，我得到不想要的警告，我看到了很多解决方法，这是因为onbeforeunload火灾之前onsubmit，这就是为什么我们不能处理它在onsubmit事件像onbeforeunload = null，但onclick事件提交按钮火灾前这两个事件，所以我更新了代码

var isChanged = false;
var isSubmit = false;

window.onbeforeunload = function (e) {
    if (isChanged && (!isSubmit)) {
        return "Make sure to save all changes.";
    }        
};

$('#submitbutton').click(function () {
    isSubmit = true;
});

$('.onchange').change(function () {
    isChanged = true;
});

简短的回答:

let pageModified = true

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