是什么导致 'beforeunload' 事件在 Chrome 中被触发？

Question

我正在添加一个事件侦听器 'beforeunload' 来检查表单是否脏了，并向我的用户提供一条消息，即离开该页面可能会导致他们丢失未保存的数据。由于我在 Chrome，我知道我不能设置自定义消息，但基本上我必须添加事件侦听器才能显示默认消息。当我的表单变脏时，该消息确实出现了，但是除了重新加载页面之外，我不知道如何重置它。我的问题是：是什么导致 'beforeunload' 事件被触发？对我来说，它只会在我的表单变脏时触发，但由于我没有设置它，所以我不确定一旦触发事件如何将其关闭。

我已经尝试在用户确认他们想要离开页面时删除事件侦听器，但是当我单击返回页面并尝试重新加载时，事件仍然会触发，即使表单没有变脏甚至 pristine 也被设置为 true。

这是控制器中的相关代码。

        var unloadEvent = function (e) {
            e.returnValue = '';
        };
        window.addEventListener("beforeunload", unloadEvent);

        // For when a user hits the back button 
        $transitions.onBefore({}, function ($transition)
        {
            console.log("on before", vm.ticketForm); 
            if (vm.ticketForm && vm.ticketForm.$dirty == true) {
                var answer = confirm("Are you sure you want to leave this page? Changes you made may not be saved.")
                if (!answer) {
                    // User would like to cancel the click and remain on the page
                    $window.history.forward(); 
                    $transition.abort();
                    return false;
                }
                else {
                    // Form is dirty but user would like to leave the page
                    // Set the form to pristine
                    window.removeEventListener("beforeunload", unloadEvent);
                    vm.ticketForm.$setPristine(); 
                    vm.ticketForm.$setUntouched(); 
                }
            }
        });

        $scope.$on('$destroy', function() {
            window.removeEventListener("beforeunload", unloadEvent); 
        });

这是 html

的一部分

 <form name="detailVM.ticketForm">
        <table class="table table-condensed table-striped table-center">
            <tbody>
                <tr>
                    <th>Username</th>
                    <th>Worker Number</th>
                    <th></th>
                    <th>Start Time</th>
                    <th>End Time</th>
                    <th>Adjusted Start Time</th>
                    <th>Adjusted End Time</th>
                    <th></th>
                </tr>

                <tr ng-repeat="worker in detailVM.currentTicket.crew_assignment.workers" ng-if="worker.revised_start_timestamp !== null && worker.revised_end_timestamp !== null">
                    <td>{{::worker.worker_username}}</td>
                    <td>{{::worker.worker_number}}</td>
                    <td><a href="#">Edit Shift</a></td>
                    <td>{{ ::detailVM.formatTime(worker.current_start_timestamp, 'MM/DD/YYYY, h:mm:ss a') }}</td>
                    <td>{{ ::detailVM.formatTime(worker.current_end_timestamp, 'MM/DD/YYYY, h:mm:ss a') }}</td>
                    <td><input type="datetime-local" ng-model="worker.revised_start_timestamp" ng-change="detailVM.changeWorkerStartTime(worker, worker.start_timestamp)"></td>
                    <td><input type="datetime-local" ng-model="worker.revised_end_timestamp" ng-change="detailVM.changeWorkerEndTime(worker, worker.end_timestmap)"></td>
                    <td>
                        <button ng-click="detailVM.deleteWorker(worker)">
                            <span class="fa fa-trash"></span>
                        </button>
                    </td>
                </tr>
                <tr ng-if="detailVM.newWorkerFormShown">
                    <td>
                        <input type="string" ng-model="detailVM.newWorkerName"/>
                    </td>
                    <td>
                        <input type="string" ng-model="detailVM.newWorkerNumber"/>
                    </td>
                    <td>
                        <input type="datetime-local" ng-model="detailVM.newWorkerStartTimestamp"/>
                    </td>
                    <td>
                        <input type="datetime-local" ng-model="detailVM.newWorkerEndTimestamp"/>
                    </td>
                    <td>
                        <button ng-click="detailVM.addWorker()">
                            <span class="fa fa-plus addButton"></span>
                        </button>
                    </td>
                </tr>
            </tbody>
        </table>
</form>

我不清楚是什么导致事件触发，因为它只是偶尔触发。据我所知，它只在表单被触摸后触发，然后即使事件侦听器被删除然后重新添加也会继续触发。

Answer 1

I am adding an event listener 'beforeunload' to check if a form is dirty or not and provide a message to my users that navigating away from the page might cause them to l ose unsaved data.

一种方法是为 form 指令创建自定义指令：

app.directive("confirmDirtyUnload", function($window) {
    return {
        require: "ngForm", 
        link: postLink,
    };
    function postLink(scope, elem, attrs, ngForm) {
        $window.addEventListener("beforeunload", checkDirty);
        elem.on("$destroy", function (ev) {
            $window.removeEventListener("beforeunload", checkDirty);
        });
        function checkDirty(event) {
            if (ngForm.$dirty) {
                 // Cancel the event as stated by the standard.
                 event.preventDefault();
                 // Chrome requires returnValue to be set.
                 event.returnValue = '';
            };
        }
    }
});

用法：

<form confirm-dirty-unload name="form1">
    <input name="text1" ng.model="data.text1" />
</form>

是什么导致 'beforeunload' 事件在 Chrome 中被触发？

What causes the 'beforeunload' event to be triggered in Chrome?

html

google-chrome

onbeforeunload

angularjs

angular-ui-router

用法：