class Home extends Component{
      componentDidMount(){
          this.props.getCustomer()     
      }   
      render(){        
          const {total, list} = this.props.customer
          console.log("total:"+total)
          console.log("list:"+list)
          return(
            <div>
              <NavBar>system</NavBar>      
              {list.map((item,index)=>(              
                <List key={index}>
                   <Item
                   arrow="horizontal"
                   thumb="https://zos.alipayobjects.com/rmsportal/dNuvNrtqUztHCwM.png"
                   multipleLine
                   onClick={() => {}}
                   >
                   name:{item.name}
                   <Brief>level:{item.level}</Brief> 
                   </Item>
                 </List>        
               ) )   
              }
            </div>
           )

Error: Cannot read property 'map' of undefine

Reason: The object calling map is undefined, and the list is undefined before the initialization of the first rendering of asynchronous data return.

the solution: make judgment on the list, an asynchronous ajax data returned list to value before rendering component.

Modify as follows:

{list && list.map((item,index)=>(              
                <List key={index}>
                   <Item
                   arrow="horizontal"
                   thumb="https://zos.alipayobjects.com/rmsportal/dNuvNrtqUztHCwM.png"
                   multipleLine
                   onClick={() => {}}
                   >
                   name:{item.name}
                   <Brief>level:{item.level}</Brief>                  
                   </Item>
                 </List>        
               ) )   
              }