优化angularjs中的ng-bind指令 [英] Optimise ng-bind directive in angularjs

问题描述

在我的角度js应用程序中，我有一个对象数组$scope.time，其中包含名称，当前时间和另一个定义的时间(以毫秒为单位). 在前端，我使用ng-bind来计算这两个时间之间的时差，并以H:m:s格式显示.请运行下面的代码.

In my angular js app I have an array of objects $scope.time which contain a name, the current time and another defined time in milliseconds. In the front-end I'm using ng-bind to calculate the difference between these two time and display it in H:m:s format. Please run the code below.

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>

当我从api获取数据时，$scope.time数组是动态的(出于演示的目的，我在此处定义了硬编码). 当我在$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，由于msTotime过滤器不断计算毫秒之间的差并将其转换为H:m:s并将其绑定到前端，因此我的浏览器开始滞后.

The $scope.time array is dynamic as I get that data from an api(I defined it hardcoded here for the purpose of demonstration). The above code works smoothly when I have a few objects in the $scope.time array. But when there are thousands of objects then my browser starts to lag as the msTotime filter keeps calculating the difference between the milliseconds and converts it to H:m:s and binds it to the frontend.

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

Now the issue is that my browser consumes 40 percent CPU when there are 1000 objects. I believe it's not an issue with ng-repeat as when I commented out <p style="display:inline-block" ng-bind="realtime | msTotime:timer.time:timer.now"> the cpu usage was just 5 percent with more than 1000 objects.

这里是否有任何方法可以优化ng-bind指令或以其他方式进行时间计算，以使msTotime过滤器完成的计算不会消耗太多的CPU.

Is there any way to optimize the ng-bind directive here or do the time calculation in some other way so that the calculations done by msTotime filter don't consume so much CPU.

推荐答案

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

I would suggest to use lodash https://lodash.com library to append the time diffrence in each object instead using directive to do that. so each time you get data from query use _.each to do the same operation and insert 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>

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