简单应用举例（2）-KnockoutJS入门指南

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Control types
这个例子，对view model没有什么特殊的展示，只是展示如何绑定到各种元素上（例如，select， radio button等）。

![](/uploads/images/20230405/af456268dee203f7a53d6e1a7ff05d9b.png)

代码: View
```
<div class="readout">
    <h3>
        What's in the model?</h3>
    <table>
        <tr>
            <td class="label">
                Text value:
            </td>
            <td data-bind="text: stringValue">
            </td>
        </tr>
        <tr>
            <td class="label">
                Password:
            </td>
            <td data-bind="text: passwordValue">
            </td>
        </tr>
        <tr>
            <td class="label">
                Bool value:
            </td>
            <td data-bind='text: booleanValue() ? "True" : "False"'>
            </td>
        </tr>
        <tr>
            <td class="label">
                Selected option:
            </td>
            <td data-bind="text: selectedOptionValue">
            </td>
        </tr>
        <tr>
            <td class="label">
                Multi-selected options:
            </td>
            <td data-bind="text: multipleSelectedOptionValues">
            </td>
        </tr>
        <tr>
            <td class="label">
                Radio button selection:
            </td>
            <td data-bind="text: radioSelectedOptionValue">
            </td>
        </tr>
    </table>
</div>
<h3>
    HTML controls</h3>
<table>
    <tr>
        <td class="label">
            Text value (updates on change):
        </td>
        <td>
            <input data-bind="value: stringValue"/>
        </td>
    </tr>
    <tr>
        <td class="label">
            Text value (updates on keystroke):
        </td>
        <td>
            <input data-bind='value: stringValue, valueUpdate: "afterkeydown"' />
        </td>
    </tr>
    <tr>
        <td class="label">
            Text value (multi-line):
        </td>
        <td>
            <textarea data-bind="value: stringValue"> </textarea>
        </td>
    </tr>
    <tr>
        <td class="label">
            Password:
        </td>
        <td>
            <input type="password" data-bind="value: passwordValue"/>
        </td>
    </tr>
    <tr>
        <td class="label">
            Checkbox:
        </td>
        <td>
            <input type="checkbox" data-bind="checked: booleanValue"/>
        </td>
    </tr>
    <tr>
        <td class="label">
            Drop-down list:
        </td>
        <td>
            <select data-bind="options: optionValues, value: selectedOptionValue">
            </select>
        </td>
    </tr>
    <tr>
        <td class="label">
            Multi-select drop-down list:
        </td>
        <td>
            <select multiple="multiple" data-bind="options: optionValues, selectedOptions: multipleSelectedOptionValues">
            </select>
        </td>
    </tr>
    <tr>
        <td class="label">
            Radio buttons:
        </td>
        <td>
            <label>
                <input type="radio" value="Alpha" data-bind="checked: radioSelectedOptionValue"/>Alpha</label>
            <label>
                <input type="radio" value="Beta" data-bind="checked: radioSelectedOptionValue"/>Beta</label>
            <label>
                <input type="radio" value="Gamma" data-bind="checked: radioSelectedOptionValue"/>Gamma</label>
        </td>
    </tr>
</table>
```
代码: View model
```
var viewModel = {
    stringValue: ko.observable("Hello"),
    passwordValue: ko.observable("mypass"),
    booleanValue: ko.observable(true),
    optionValues: ["Alpha", "Beta", "Gamma"],
    selectedOptionValue: ko.observable("Gamma"),
    multipleSelectedOptionValues: ko.observable(["Alpha"]),
    radioSelectedOptionValue: ko.observable("Beta")
};

ko.applyBindings(viewModel);
```
6   Templating
这个例子展示的render模板，以及在模板内部如何使用data binding属性的。

Template很容易嵌套，当任何依赖数据改变的时候，Knockout会自动重新render模板。参考演示（启用‘Show render times’），Knockout知道只需要重新render改变的那些数据所绑定的最近的模板。

![](/uploads/images/20230405/a6ed8142245e79344e040eb2a080e7d3.png)

代码: View
```
<div data-bind='template: "peopleTemplate"'>
</div>
<label>
    <input type="checkbox" data-bind="checked: showRenderTimes"/>
    Show render times</label>
<script type="text/html" id="peopleTemplate">
<h2>People</h2>
<ul>
  {{each people}}
  <li>
  <div>
    ${ name } has <span data-bind="text: children().length">&nbsp;</span> children:
    <a href="#" data-bind="click: addChild ">Add child</a>
    <span class="renderTime" data-bind="visible: showRenderTimes">
                        (person rendered at <span data-bind="text: new Date().getSeconds()"></span>)
    </span>
  </div>
  <div data-bind='template: { name: "childrenTemplate", data: children }'></div>
  </li>
{{/each}}
</ul>
</script>
<script type="text/html" id="childrenTemplate">
    <ul>
        {{each $data}}
            <li>
                ${ this }
                <span class="renderTime" data-bind="visible: viewModel.showRenderTimes">
                    (child rendered at <span data-bind="text: new Date().getSeconds()"></span>)
               </span>
           </li>
        {{/each}}
</ul>
</script>
```
代码: View model
```
// Define a "person" class that tracks its own name and children, and has a method to add a new child

var person = function (name, children) {
    this.name = name;
    this.children = ko.observableArray(children);

this.addChild = function () {
        this.children.push("New child");
    } .bind(this);
}

// The view model is an abstract description of the state of the UI, but without any knowledge of the UI technology (HTML)

var viewModel = {
    people: [
        new person("Annabelle", ["Arnie", "Anders", "Apple"]),
        new person("Bertie", ["Boutros-Boutros", "Brianna", "Barbie", "Bee-bop"]),
        new person("Charles", ["Cayenne", "Cleopatra"])
    ],
    showRenderTimes: ko.observable(false)
};

ko.applyBindings(viewModel);
```
7   Paged grid
data-bind="..."绑定（像text, visible, 和click不是固定死的） - 你可以很容易自定义自己的绑定。如果你的自定义绑定仅仅是添加事件或者更新DOM元素的属性，那几行就可以实现。不过，你依然可以自定义可以重用的绑定（或插件），就行本例的simpleGrid绑定。

如果一个插件需要自己标准的view model（例如本例的ko.simpleGrid.viewModel ），它提供既提供了该如何配置插件实例（分页大小，列声明）工作，也提供了view model上的属性是否是observable 的（例如currentpage索引）。也可以扩展代码让这些属性很容易地改变，并且让UI自动更新。例如，“Jump to first page”按钮的工作原理。

查看HTML源代码可以看到非常容易使用这个simple grid插件。simpleGrid源码地址是：http://knockoutjs.com/examples/resources/knockout.simpleGrid.js
![](/uploads/images/20230405/9dcf2325f9c5fa46ca046693c974d5d3.png)

代码: View
```
<div data-bind="simpleGrid: gridViewModel"> </div>

<button data-bind="click: function() { gridViewModel.currentPageIndex(0) }">
    Jump to first page
</button>
```
代码: View model
```
var myModel = {
    items: ko.observableArray([
        { name: "Well-Travelled Kitten", sales: 352, price: 75.95 },
        { name: "Speedy Coyote", sales: 89, price: 190.00 },
        { name: "Furious Lizard", sales: 152, price: 25.00 },
        { name: "Indifferent Monkey", sales: 1, price: 99.95 },
        { name: "Brooding Dragon", sales: 0, price: 6350 },
        { name: "Ingenious Tadpole", sales: 39450, price: 0.35 },
        { name: "Optimistic Snail", sales: 420, price: 1.50 }
    ]),

sortByName: function () {
        this.items.sort(function (a, b) {
            return a.name < b.name ? -1 : 1;
        });
    }
};

myModel.gridViewModel = new ko.simpleGrid.viewModel({
    data: myModel.items,
    columns: [
        { headerText: "Item Name", rowText: "name" },
        { headerText: "Sales Count", rowText: "sales" },
        { headerText: "Price", rowText: function (item) { return "$" + item.price.toFixed(2) } }
    ],
    pageSize: 4
});

ko.applyBindings(myModel);
```
8   Animated transitions
该例子展示了2种方式实现动画过渡效果：

当使用template/foreach绑定的时候，你可以使用afterAdd和beforeRemove回调函数，他们可以让你写代码真实操作添加和删除元素，这样你就可以使用像jQuery的 slideUp/slideDown()这样的动画效果。在planet types之间切换或添加新的planet可以看到效果。

通过observable 类型的值，我们不难定义自己的Knockout绑定，查看HTML源代码可以看到一个自定义绑定fadeVisible，不管什么时候它改变了， jQuery就会在相关的元素上执行fadeIn/fadeOut动画效果。点击“advanced options” checkbox 可以看到效果。

![](/uploads/images/20230405/fb37a68d9eefdbb6f2271d26f87d1680.png)

代码: View
```
<h2>Planets</h2>
<p>
    <label>
        <input type="checkbox" data-bind="checked: displayAdvancedOptions"/>
        Display advanced options
    </label>
</p>
<p data-bind="fadeVisible: displayAdvancedOptions">
    Show:
    <label><input type="radio" value="all" data-bind="checked: typeToShow"/>All</label>
    <label><input type="radio" value="rock" data-bind="checked: typeToShow"/>Rocky planets</label>
    <label><input type="radio" value="gasgiant" data-bind="checked: typeToShow"/>Gas giants</label>
</p>
<div data-bind='template: { name: "planetsTemplate",
                            foreach: planetsToShow,
                            beforeRemove: function(elem) { $(elem).slideUp(function() { $(elem).remove(); }) },
                            afterAdd: function(elem) { $(elem).hide().slideDown() } }'>
</div>
<script type="text/html" id="planetsTemplate">
    <div class="planet ${ type }">${ name }</div>
</script>
<p data-bind="fadeVisible: displayAdvancedOptions">
    <button data-bind='click: function() { addPlanet("rock") }'>
        Add rocky planet</button>
    <button data-bind='click: function() { addPlanet("gasgiant") }'>
        Add gas giant</button>
</p>
```
代码: View model
```
var viewModel = {
    planets: ko.observableArray([
        { name: "Mercury", type: "rock" },
        { name: "Venus", type: "rock" },
        { name: "Earth", type: "rock" },
        { name: "Mars", type: "rock" },
        { name: "Jupiter", type: "gasgiant" },
        { name: "Saturn", type: "gasgiant" },
        { name: "Uranus", type: "gasgiant" },
        { name: "Neptune", type: "gasgiant" },
        { name: "Pluto", type: "rock" }
    ]),

typeToShow: ko.observable("all"),
    displayAdvancedOptions: ko.observable(false),

addPlanet: function (type) { this.planets.push({ name: "New planet", type: type }); }
};

viewModel.planetsToShow = ko.dependentObservable(function () {
    // Represents a filtered list of planets
    // i.e., only those matching the "typeToShow" condition

var desiredType = this.typeToShow();

if (desiredType == "all")
        return this.planets();

return ko.utils.arrayFilter(this.planets(), function (planet) {
        return planet.type == desiredType;
    });
} .bind(viewModel));

// Here's a custom Knockout binding that makes elements shown/hidden via jQuery's fadeIn()/fadeOut() methods
// Could be stored in a separate utility library

ko.bindingHandlers.fadeVisible = {
    init: function (element, valueAccessor) {
        // Initially set the element to be instantly visible/hidden depending on the value
        var value = valueAccessor();

$(element).toggle(ko.utils.unwrapObservable(value));
        // Use "unwrapObservable" so we can handle values that may or may not be observable
    },

update: function (element, valueAccessor) {
        // Whenever the value subsequently changes, slowly fade the element in or out
        var value = valueAccessor();
        ko.utils.unwrapObservable(value) ? $(element).fadeIn() : $(element).fadeOut();
    }
};

ko.applyBindings(viewModel);
```