Knockout学习笔记之二（$root，$parent及$data的区别）

创建时间：2017-05-24 投稿人：浏览次数：1381

以下是我从Google上找到的一个例子，非常生动形象，我修改了部分代码，具体内容如下：

对于$root 与$parent的区别：

$root refers to the view model applied to the DOM with ko.applyBindings;

译：$root 是指ViewModel所应用于ko.applyBindings时所使用的DOM;

$parent refers to the immediate outer scope;

　　译：$parent 是指当前DOM元素直接的外部父类（只有一层）;

Or, visually, from $data"s perspective:

Or, in words of the relevant documentation:

$parent: This is the view model object in the parent context, the one immeditely outside the current context.
$root: This is the main view model object in the root context, i.e., the topmost parent context. It’s usually the object that was passed to ko.applyBindings. It is equivalent to $parents[$parents.length - 1].

对于三者的区别（$root，$parent及$data）：

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
    <title></title>
    <script type="text/javascript" src="knockout-3.4.0.js"></script>
    <style>
        th, td {
            padding: 10px;
            border: 1px solid gray;
        }
    </style>
    <script type="text/javascript">
        window.onload = function () {
            vm.mainPerson(grandpa);
            grandpa.children.push(daddy);
            daddy.children.push(son1);
            daddy.children.push(son2);
            ko.applyBindings(vm);
        }
        
        var Person = function (name) {
            var self = this;
            self.name = ko.observable(name);
            self.children = ko.observableArray([]);
        }

        var ViewModel = function () {
            var self = this;
            self.name = "root view model";
            self.mainPerson = ko.observable();
        }

        var vm;
        vm= new ViewModel(),
        grandpa = new Person("grandpa"),
        daddy = new Person("daddy"),
        son1 = new Person("marc"),
        son2 = new Person("john");
    </script>
    <script type="text/html" id="person">
        <tr>
            <td data-bind="text: $root.name"></td>
            <td data-bind="text: $parent.name"></td>
            <td data-bind="text: $data.name"></td>
        </tr>
        <!-- ko template: { name: "person", foreach: children } --><!-- /ko -->
    </script>

    <table>
        <tr>
            <th>$root</th>
            <th>$parent</th>
            <th>$data</th>
        </tr>
        <!-- ko template: { name: "person", data: mainPerson } --><!-- /ko -->
    </table>
</head>
<body>
</body>
</html>

View Code

具体页面呈现：

The $root is always the same. The $parent is different, depending on how deeply nested you are.

译：$root经常是相同的，而$parent是不同的，而这种不同主要取决于你嵌套的深度。

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