优化 angularjs 中的 ng-bind 指令

Question

在我的 Angular js 应用程序中，我有一个对象数组$scope.time，其中包含一个名称、当前时间和另一个以毫秒为单位的定义时间。 在前端，我使用ng-bind 计算这两个时间之间的差异并以 H:m:s 格式显示。请运行以下代码。

var app = angular.module('angularapp', []);
app.filter("msTotime", function() {
  return function(timee,started,ended) {
    var startDate = new Date(started);
    var endDate = new Date(ended);
    var milisecondsDiff = endDate - startDate;
    var final = Math.floor(milisecondsDiff/(1000*60*60)).toLocaleString(undefined, {minimumIntegerDigits: 2}) + ":" + (Math.floor(milisecondsDiff/(1000*60))%60).toLocaleString(undefined, {minimumIntegerDigits: 2})  + ":" + (Math.floor(milisecondsDiff/1000)%60).toLocaleString(undefined, {minimumIntegerDigits: 2}) ;
    var defaulttime = '00:00:00';
    if(final == '-01:-01:-01'){
    return  defaulttime;
    }
    else {
    return final;
  }
}
});
app.controller('list', function($scope,$window) {
$scope.time = [{"game":"Halo","now":1554805270181,"time":1554794475267},
{"game":"CODuty","now":1554805270181,"time":1554802957031},
{"game":"WOF","now":1554805270181,"time":1554732154093},
{"game":"WarCraft","now":1554805270181,"time":1554803456875},
{"game":"POP","now":1554805270181,"time":1554803456275},
{"game":"RedBulls","now":1554805270181,"time":1554800620012},
{"game":"Eragon","now":1554805270181,"time":1554433320072}];
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/angular.js/1.5.10/angular.min.js"></script>
<div ng-app="angularapp">
<div ng-controller="list" >
<div ng-repeat="timer in time">
<h5>{{timer.game}}</h5><hr>
Milliseconds to H:M:S for  {{timer.game}} <p style="display:inline-block" ng-bind="realtime | msTotime:timer.time:timer.now"></p><br>
</div>
</div>
</div>

$scope.time 数组是动态的，因为我从 api 获取数据（为了演示的目的，我在这里对其进行了硬编码）。 当我在$scope.time 数组中有几个对象时，上面的代码可以顺利运行。但是当有数千个对象时，我的浏览器开始滞后，因为msTotime 过滤器不断计算毫秒之间的差异并将其转换为H:m:s 并将其绑定到前端。

现在的问题是，当有 1000 个对象时，我的浏览器会消耗 40% 的 CPU。我相信ng-repeat 不是问题，因为当我注释掉<p style="display:inline-block" ng-bind="realtime | msTotime:timer.time:timer.now"> 时，CPU 使用率只有 5%，对象超过 1000 个。

有没有什么办法可以优化这里的ng-bind指令或者以其他方式进行时间计算，这样msTotime过滤器所做的计算就不会消耗太多的CPU。

Answer 1

我建议使用 lodash https://lodash.com 库在每个对象中附加时间差异，而不是使用 directive 来做到这一点。因此，每次从查询中获取数据时，请使用 _.each 执行相同的操作并插入 var realtime。

var app = angular.module('angularapp', []);

app.controller('list', function($scope,$window) {

  $scope.time = [
    {"game":"Halo","now":1554805270181,"time":1554794475267},
    {"game":"CODuty","now":1554805270181,"time":1554802957031},
    {"game":"WOF","now":1554805270181,"time":1554732154093},
    {"game":"WarCraft","now":1554805270181,"time":1554803456875},
    {"game":"POP","now":1554805270181,"time":1554803456275},
    {"game":"RedBulls","now":1554805270181,"time":1554800620012},
    {"game":"Eragon","now":1554805270181,"time":1554433320072}
  ];

  _.each($scope.time, function(obj, index){   
      var startDate = new Date(obj.time);
      var endDate = new Date(obj.now);
      var milisecondsDiff = endDate - startDate;
      var final = Math.floor(milisecondsDiff / (1000 * 60 * 60)).toLocaleString(undefined, {
        minimumIntegerDigits: 2
      }) + ":" + (Math.floor(milisecondsDiff / (1000 * 60)) % 60).toLocaleString(undefined, {
        minimumIntegerDigits: 2
      }) + ":" + (Math.floor(milisecondsDiff / 1000) % 60).toLocaleString(undefined, {
        minimumIntegerDigits: 2
      });
      var defaulttime = '00:00:00';
      if (final == '-01:-01:-01') {
        obj.realtime = defaulttime;
      } else {
        obj.realtime = final;
      }
  });
    
  
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/angular.js/1.5.10/angular.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.11/lodash.core.min.js"></script>

<div ng-app="angularapp">
<div ng-controller="list" >
<div ng-repeat="timer in time">
<h5>{{timer.game}}</h5><hr/>
Milliseconds to H:M:S for {{timer.game}} <p style="display:inline-block;">{{timer.realtime}}</p><br>
</div>
</div>
</div>