React將屬性添加到不可變的對象

Question

我試圖添加一個新的屬性到數組中的對象。我的想法是做這樣的事情：

class Foo extends Component { 
    constructor(props) { 
     super(props); 

     this.state = this.getInitialState(); 
     console.log(this.state); //Property "label" is missing in "members" array 
    } 

    /** 
    * Get initial state 
    * @returns {{title, description}} 
    */ 
    getInitialState =() => { 
     let members = this.props.members.slice(); 
     members.map((member) => { 
      return { 
       ...member, 
       label: (member.firstName + " " + member.lastName) 
      } 
     }); 
     console.log(members); //"label" is not a property of objects 

     return {title: "", description: "", responsible: [], typeOf: null, 
       members: members}; 
    }; 

    render() { 
     return (<div/>) 
    } 
} 

我想members留/保持不變，但這個陣列中添加另一個屬性對每個對象。我在這裏做錯了什麼？謝謝！

Answer 1

你不存儲返回地圖的價值，成員變量

getInitialState =() => { 
     let members = this.props.members.map((member) => { 
      return { 
       ...member, 
       label: (member.firstName + " " + member.lastName) 
      } 
     }); 
     console.log(members); //"label" is not a property of objects 

     return {title: "", description: "", responsible: [], typeOf: null, 
       members: members}; 
    }; 

Answer 2

數組原型.map()不發生變異原數組，而是返回一個新的數組。