CODEWITHSUNDEEP
javascriptknockout.js
desmondlee
desmondlee

Reputation: 1703

track number of evaluations in knockout

I would like to know how to I track the number of evaluation in knockout observable array for GetArray1() and GetArray2() below. I have read a sample from this fiddle link but not sure how to fit it into this situation.

var data1 = [{
    "Hours": 1
}, {
    "Hours": 2
}, {
    "Hours": 3
}];


function ViewModel() {
    var self = this;
    self.sampleArray = ko.observableArray([]);
  
   var newData = ko.mapping.fromJS(data1)();
    self.GetArray = function() {
       ko.utils.arrayForEach(newData, function (item) {
          self.sampleArray.push(item) //push here
       });
    }
    
    self.GetArray2 = function() {
       $.each(newData, function (index, value) {
          self.sampleArray.push(value) //push here
       });
    }
    
    self.GetArray();
  self.GetArray2();
}
ko.applyBindings(new ViewModel())
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/knockout/3.2.0/knockout-min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/knockout.mapping/2.4.1/knockout.mapping.min.js"></script>

<div data-bind="foreach:sampleArray">
    <p data-bind="text:Hours"></p>
    <br/>
</div>

Upvotes: 0

Views: 77

Answers (1)

super cool
super cool

Reputation: 6045

well in the link you provided they are creating a function using fn which has the computation logic for getting the re-evaluation count

Better way would be using inbuilt functions isInitial and getDependenciesCount of computed under computedContext .

Logic :

 ko.computed(function () {
     var subscribe = self.sampleArray(); //declared on top to subscribe initially
     if (ko.computedContext.isInitial()) return true;
     var count = ko.computedContext.getDependenciesCount();
     self.revaluationCount(self.revaluationCount() + count);
 });

As per Docs :

isInitial() — A function that returns true if called during the first ever evaluation of the current computed observable, or false otherwise. For pure computed observables, isInitial() is always undefined.

getDependenciesCount() — Returns the number of dependencies of the computed observable detected so far during the current evaluation.

Check here for complete documentation .

working sample with complete code here

Upvotes: 1

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