javascript - 使用 ko.mapping.fromJS 保留原始值

Question

我有一个定义为 ko.observableArray([]) 的值，并使用 ko.mapping.fromJS 将来自 ajax 的数据附加到其中。但是，当我再次使用 ko.mapping.fromJS 时，从 ajax 调用获取的新数据将替换 self.SampleArray 而不是附加新数据。我想保留以前的数据。怎么可能做到呢？

function ViewModel() {
  var self = this;
  
  self.SampleArray = ko.observableArray([]);
  
  $.ajax({
    ..
    ..
    success: function() {       
       ko.mapping.fromJS(data, {}, self.sampleArray());
    }
  })
}

Answer 1

尝试将其插入 observableArray 而不是替换它

View 模型:

function ViewModel() {
    var self = this;
    self.sampleArray = ko.observableArray([{
        'Hours': 0.5
    }])
    setTimeout(function () {
        alert('Mock of ajax call')
        var newData = ko.mapping.fromJS(data1)();
        self.sampleArray.push.apply(self.sampleArray,newData) 
    }, 2000);
}
ko.applyBindings(new ViewModel())

push.apply 相对于传统循环语句的优势:

If your array / collection has multiple items and if you add (array.push(item) one by one then the subscribers will be notified for each and every push / add operation. Then the UI will have that number of refresh. That will hurt the UI page performances.

But if you use array.push.appy , then you can still add multiple items, but subscribers will be notified only once.

That is the difference and the advantage / usage of this array.push.apply function.

示例工作 fiddle here

使用 utils.forEach 的示例工作 fiddle here