當我執行下面的代碼時，它會給我上面的錯誤？

Question

Uncaught ReferenceError: Unable to process binding "value: function(){return sumValBinding }" Message: sumValBinding is not defined 

這裏我的HTML：

<div class="form-group"> 
       <label for="inputdefault">First number</label> 
       <input class="form-control" id="Textbox1" type="text"> 
      </div> 
      <div class="form-group"> 
       <label for="inputdefault">Second number</label> 
       <input class="form-control" id="Textbox2" type="text"> 
      </div> 
      <div class="form-group"> 
       <label for="inputdefault">Answer</label> 
       <input class="form-control" id="TextboxSum" type="number" data-bind="value:sumValBinding"> 
      </div> 
      <button type="button" class="btn btn-default" id="submit">Submit</button> 

================================== ============================================ 在這裏Javascript/Knockout JS enter code here

$("#submit").click(function (e) { 
     debugger; 
     number1 = parseInt(document.getElementById("Textbox1").value); 
     number2 = parseInt(document.getElementById("Textbox2").value); 
     sumOfTwoNumber = number1 + number2; 
     console.log(parseInt(number2)); 
     //v = new viewModel(); 
     ko.applyBindings(new viewModel(), document.getElementById("TextboxSum")); 
    }); 
    var viewModel = function() 
    { 
     sumValBinding: ko.observable(sumOfTwoNumber) // Prepopulate 
     }; 

Answer 1

您的視圖模型是一個構造函數，因此，你應該，如果你想擁有它的一個對象實例的屬性分配給此：

var viewModel = function() { 
    this.sumValBinding = ko.observable(sumOfTwoNumber); 
}; 

或你的構造可以返回一個對象：

var viewModel = function() { 
    return { 
     sumValBinding: ko.observable(sumOfTwoNumber); 
    }; 
};