Javascript ReactJS如何从列表中删除项目

ReactJS how to delete item from list

提问by Denys

I have have code that creates <li>elements. I need to delete elements one by one by clicking. For each element I have Delete button. I understand that I need some function to delete items by id. How to do this function to delete elements in ReactJS? My code:

我有创建<li>元素的代码。我需要通过点击一一删除元素。对于我拥有的每个元素Delete button。我知道我需要一些功能来删除项目id。如何做这个功能来删除 ReactJS 中的元素？我的代码：

class TodoApp extends React.Component {
    constructor(props) {
        super(props);
        this.handleChange = this.handleChange.bind(this);
        this.handleSubmit = this.handleSubmit.bind(this);
        this.state = {items: [], text: ''};
    }

    render() {
        return (
            <div>
                <h3>TODO</h3>
                <TodoList items={this.state.items} />
                <form onSubmit={this.handleSubmit}>
                    <input onChange={this.handleChange} value={this.state.text} />
                    <button>{'Add #' + (this.state.items.length + 1)}</button>
                </form>
            </div>
        );
    }

    handleChange(e) {
        this.setState({text: e.target.value});
    }

    handleSubmit(e) {
        e.preventDefault();
        var newItem = {
            text: this.props.w +''+this.props.t,
            id: Date.now()
        };
        this.setState((prevState) => ({
            items: prevState.items.concat(newItem),
            text: ''
        }));
    }

    delete(id){          // How that function knows id of item that need to delete and how to delete item?
        this.setState(this.item.id)
    }
}

class TodoList extends React.Component {
    render() {
        return (
            <ul>
                {this.props.items.map(item => (
                    <li key={item.id}>{item.text}<button onClick={this.delete.bind(this)}>Delete</button></li>
                ))}
            </ul>
        );
    }
}

回答by Mayank Shukla

You are managing the data in Parent component and rendering the UI in Child component, so to delete item from child component you need to pass a function along with data, call that function from child and pass any unique identifier of list item, inside parent component delete the item using that unique identifier.

您正在管理父组件中的数据并在子组件中呈现 UI，因此要从子组件中删除项目，您需要传递一个函数和数据，从子组件调用该函数并在父组件内部传递列表项的任何唯一标识符使用该唯一标识符删除项目。

Step1:Pass a function from parent component along with data, like this:

Step1：从父组件传递一个函数和数据，像这样：

<TodoList items={this.state.items} _handleDelete={this.delete.bind(this)}/>

Step2:Define deletefunction in parent component like this:

Step2：delete在父组件中定义函数，如下所示：

delete(id){
    this.setState(prevState => ({
        data: prevState.data.filter(el => el != id )
    }));
}

Step3:Call that function from child component using this.props._handleDelete():

步骤 3：使用this.props._handleDelete()以下方法从子组件调用该函数：

class TodoList extends React.Component {

    _handleDelete(id){
        this.props._handleDelete(id);
    }

    render() {
        return (
            <ul>
                {this.props.items.map(item => (
                    <li key={item.id}>{item.text}<button onClick={this._handleDelete.bind(this, item.id)}>Delete</button></li>
                ))}
            </ul>
        );
    }
}

Check this working example:

检查这个工作示例：

class App extends React.Component{
   constructor(){
      super();
      this.state = {
        data: [1,2,3,4,5]
      }
      this.delete = this.delete.bind(this);
   }
   
   delete(id){
      this.setState(prevState => ({
          data: prevState.data.filter(el => el != id )
      }));
   }
   
   render(){
      return(
          <Child delete={this.delete} data={this.state.data}/>
      );
   }
}

class Child extends React.Component{

   delete(id){
       this.props.delete(id);
   }
   
   render(){
      return(
         <div>
           {
              this.props.data.map(el=>
                  <p onClick={this.delete.bind(this, el)}>{el}</p>
              )
           }
         </div>
      )
   }
}

ReactDOM.render(<App/>, document.getElementById('app'))

<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'/>