我想检查状态的真值并相应地设置一个类。下面的代码就是这样做的,但是...
有没有办法以编程方式执行此操作,也许可以通过for循环来添加所有内联函数检查。
这样做的原因是,在某些情况下,我有数百个项目,并且我不愿重复并粘贴相同的代码数百次。
class App extends React.Component {
constructor() {
super();
this.state = {
item1: false,
item2: true,
item3: false
}
}
render() {
return(
<div className="app">
<ul>
<li data-item="item1" className={(this.state.item1) ? "active" : null}>Item 1</li>
<li data-item="item2" className={(this.state.item2) ? "active" : null}>Item 2</li>
<li data-item="item3" className={(this.state.item3) ? "active" : null}>Item 3</li>
</ul>
</div>
);
}
}
ReactDOM.render(<App />, document.getElementById('app'));
.active {
color: green;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react-dom.min.js"></script>
<div id="app"></div>
最佳答案
如果有成千上万个,则它们可能应该位于数组而不是对象中。但是,如果需要,我们可以将对象的属性名称作为数组获取。
改用数组(请参见注释):
class App extends React.Component {
constructor() {
super();
// Turning items into an array
this.state = {
items: [
{name: "item1", label: "Item 1", state: false},
{name: "item2", label: "Item 2", state: true},
{name: "item3", label: "Item 3", state: false}
]
};
}
render() {
return(
<div className="app">
<ul>
{/* Loop through the items, outputting them*/}
{this.state.items.map(item => (
<li data-item={item.name} className={item.state ? "active" : null}>{item.label}</li>
))}
</ul>
</div>
);
}
}
ReactDOM.render(<App />, document.getElementById('app'));
.active {
color: green;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react-dom.min.js"></script>
<div id="app"></div>
使用您现有的对象加上另一个对象为我们提供项目标签(请参阅注释):
class App extends React.Component {
constructor() {
super();
this.state = {
item1: false,
item2: true,
item3: false
};
// The labels we want on the items
this.itemNames = {
item1: "Item 1",
item2: "Item 2",
item3: "Item 3"
};
}
render() {
return(
<div className="app">
<ul>
{/* Loop through the items, outputting them*/}
{Object.keys(this.state).map(key => (
<li data-item={key} className={this.state[key] ? "active" : null}>{this.itemNames[key]}</li>
))}
</ul>
</div>
);
}
}
ReactDOM.render(<App />, document.getElementById('app'));
.active {
color: green;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react-dom.min.js"></script>
<div id="app"></div>