当我运行此 html 页面并单击选择元素中的某个选项时，价格值会自动更改。怎么可能？您能解释一下 select elementvalue:meal, 的功能以及在这里发挥的作用吗？
<!DOCTYPE html>
<html lang="en" xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta charset="utf-8" />
<title>Working with Lists and Collections</title>
<script type="text/javascript" src="knockout-3.1.0.debug.js"></script>
<script type="text/javascript">
function SeatReservation(name, initialMeal) {
var self = this;
self.name = name;
self.meal = ko.observable(initialMeal);
}
// Overall viewmodel for this screen, along with initial state
function ReservationsViewModel() {
var self = this;
// Non-editable catalog data - would come from the server
self.availableMeals = [
{ mealName: "Standard (sandwich)", price: 0 },
{ mealName: "Premium (lobster)", price: 34.95 },
{ mealName: "Ultimate (whole zebra)", price: 290 }
];
// Editable data
self.seats = ko.observableArray([
new SeatReservation("Steve", self.availableMeals[0]),
new SeatReservation("Bert", self.availableMeals[0])
]);
// Operations
self.addSeat = function () {
self.seats.push(new SeatReservation("", self.availableMeals[0]));
}
}
</script>
</head>
<body>
<div>
<h2>Your seat reservations</h2>
<table>
<thead>
<tr>
<th>Passenger name</th>
<th>Meal</th>
<th>Surcharge</th>
<th></th>
</tr>
</thead>
<tbody data-bind="foreach: seats">
<tr>
<td>
<input data-bind="value: name" /></td>
<td>
<select data-bind="options: $root.availableMeals, value: meal, optionsText: 'mealName'"></select></td>
<td data-bind="text: meal().price"></td>
</tr>
</tbody>
</table>
<button data-bind="click: addSeat">Reserve another seat</button>
</div>
<script type="text/javascript">
ko.applyBindings(new ReservationsViewModel());
</script>
</body>
</html>
最佳答案
这就是 knockout 的设计原理。我建议浏览Knockout Tutorials以便更好地理解它。
但是为了回答您的问题，您的select设置为显示:$root.availableMeals，它是所有餐食的数组，定义为:
self.availableMeals = [
{ mealName: "Standard (sandwich)", price: 0 },
{ mealName: "Premium (lobster)", price: 34.95 },
{ mealName: "Ultimate (whole zebra)", price: 290 }
];
数组中的每个项目都有 2 个属性:mealName，它是 select 中的显示值和 price，它用于附加费列。显示值设置为:optionsText: 'mealName'。
您的 UI 允许您从此列表中选择一个选项，并使用以下选项保存选择:值:餐，它被定义为每个座位预订的可观察值，定义为默认值:
self.meal = ko.observable(initialMeal);
一旦做出选择并且该值已更新， knockout 就会开始处理要在附加费列上显示的值。
由于餐食选择已更新且可观察，因此价格会自动更改以与餐食选择一致，因为您的绑定(bind)配置为返回价格预订座位时选择的餐食。
<td data-bind="text: meal().price"></td>
JSFiddle For Reference
关于javascript - 使用 Knockout.JS 进行可观察绑定(bind)，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/24491731/