Jquery KnockOutJS将两个文本框值添加到一起

我所要做的就是让KnockOut将两个文本框的值相加，然后将结果放入第三个文本框

我这里有一个JSFIDLE：

我的HTML框是：

<input data-bind="value:AirportPickup" data-val="true" data-val-number="The field Airport Pickup £10 per person must be a number." data-val-required="The Airport Pickup £10 per person field is required." id="AirportPickup" name="AirportPickup" type="text" value="0" />

<input data-bind="value:PackedLunch" data-val="true" data-val-number="The field Packed Lunch £6.50 must be a number." data-val-required="The Packed Lunch £6.50 field is required." id="PackedLunch" name="PackedLunch" type="text" value="0" />

<input data-bind="value:Breakfast" data-val="true" data-val-number="The field Breakfast £6.00 must be a number." data-val-required="The Breakfast £6.00 field is required." id="Breakfast" name="Breakfast" type="text" value="0" />

但是，当我在前两个文本框中输入任何内容时，什么也没有发生

有人能帮忙吗

谢谢

使用：

请注意，此代码需要一些验证（例如，确保输入是一个数字）。

使用：

---

请注意，此代码需要一些验证（例如，确保输入是一个数字）。

此代码需要是一个计算的可观察值：

this.Breakfast = ko.computed(function() {
 return this.AirportPickup + this.PackedLunch;
});

---

这个。早餐需要是一个计算的可观察的：

this.Breakfast = ko.computed(function() {
 return this.AirportPickup + this.PackedLunch;
});

另一种可能是

只需在数据绑定中设置值

 <input data-bind="value:AirportPickup" data-val="true" data-val-number="The field Airport Pickup £10 per person must be a number." data-val-required="The Airport Pickup £10 per person field is required." id="AirportPickup" name="AirportPickup" type="text" value="0" />

<input data-bind="value:PackedLunch" data-val="true" data-val-number="The field Packed Lunch £6.50 must be a number." data-val-required="The Packed Lunch £6.50 field is required." id="PackedLunch" name="PackedLunch" type="text" value="0" />

<input data-bind="value:Number(AirportPickup()) + Number( PackedLunch())" data-val="true" data-val-number="The field Breakfast £6.00 must be a number." data-val-required="The Breakfast £6.00 field is required." id="Breakfast" name="Breakfast" type="text" value="0" />;

;

另一种方法是

只需在数据绑定中设置值

 <input data-bind="value:AirportPickup" data-val="true" data-val-number="The field Airport Pickup £10 per person must be a number." data-val-required="The Airport Pickup £10 per person field is required." id="AirportPickup" name="AirportPickup" type="text" value="0" />

<input data-bind="value:PackedLunch" data-val="true" data-val-number="The field Packed Lunch £6.50 must be a number." data-val-required="The Packed Lunch £6.50 field is required." id="PackedLunch" name="PackedLunch" type="text" value="0" />

<input data-bind="value:Number(AirportPickup()) + Number( PackedLunch())" data-val="true" data-val-number="The field Breakfast £6.00 must be a number." data-val-required="The Breakfast £6.00 field is required." id="Breakfast" name="Breakfast" type="text" value="0" />;

;