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30-seconds-of-code/snippets/Tabs.md
2019-01-27 17:59:52 +08:00

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### Tab
Render a menu and a view, change the content in the view by clicking the button in the menu and the callback will execute before render
Define the `TabItem` as a middleware, pass it to the `Tab` and remove the useless nodes expect `TabItem` by identify the function's name in `props.children`, after that we will use the collected nodes to render the `tab-menu` and `tab-view` with map. Buttons in the `tab-menu` will execute `changeTab`
when been clicked, `changeTab` will execute the callback funciton(`onTabClick`) and change `bindIndex` to emit `render`,every node in `tab-view` use `bindIndex` and the `index` which ws passing from `TabItem` to judege whether it show of not(`itemStyle`)
```jsx
class Tab extends React.Component{
constructor(props){
super(props)
this.changeTab(props.defaultIndex)
this.state = {
bindIndex:''
}
}
changeTab(newIndex){
if(typeof this.props.onTabClick === 'function'){
this.props.onTabClick(newIndex)
}
this.setState({
bindIndex: newIndex
})
}
itemStyle(index){
return {
display:this.state.bindIndex === index?'block':'none'
}
}
render(){
const items = this.props.children
.filter(item=>item.type.name==='TabItem')
return (
<div className='wrapper'>
<div className='tab-menu'>
{items.map(({props:{index, label}})=><button onClick={()=>this.changeTab(index)}>{label}</button>)}
</div>
<div className='tab-view'>
{items.map(({props})=>(
<div {...props}
className='tab-view_item'
key={props.index}
style={this.itemStyle(props.index)}/>))}
</div>
</div>
)
}
}
function TabItem(props){
return <div {...props}></div>
}
```
```jsx
ReactDOM.render(
<Tab defaultIndex='1' onTabClick={console.log}>
<TabItem label='item1' index='1'>item1</TabItem>
<TabItem label='item2' index='2'>item2</TabItem>
</Tab>,
document.getElementById('root')
);
```
<!-- tags: visual,children,class -->
<!-- expertise: 1 -->