在 React 中调用 API - item.map 不是函数

Question

I am currently making a hockey application using an API from NHL.

I am new to React and I always get the mistake item.map is not a function.

import React, {Component} from 'react';

class Api extends Component {
  constructor(props) {
    super(props);
    this.state = {
      error: null,
      isLoaded: false,
      items: []
    };
  }

  componentDidMount() {
    fetch("https://statsapi.web.nhl.com/api/v1/divisions/1")
      .then(res => res.json())
      .then(
        (result) => {
          this.setState({
            isLoaded: true,
            items: result.items
          });
        },
        // Note: it's important to handle errors here
        // instead of a catch() block so that we don't swallow
        // exceptions from actual bugs in components.
        (error) => {
          this.setState({
            isLoaded: true,
            error
          });
        }
      )
  }



  render() {
    const { error, isLoaded, items } = this.state;
    if (error) {
      return <div>Error: {error.message}</div>;
    } else if (!isLoaded) {
      return <div>Loading...</div>;
    } else {
      return (
          <ul>
          <li key={item.id}>{item.name}</li>
          </ul>
      );
    }
  }

}

export default Api

The error is definitely in the render function but I can't seem to be able to fix it!

Answer 1

You are not calling items.map() anywhere. Try this one:

    render() {
        const { error, isLoaded, items } = this.state;
        if (error) {
            return <div>Error: {error.message}</div>;
        } else if (!isLoaded) {
            return <div>Loading...</div>;
        } else {
            return (
                <React.Fragment>
                    <ul>
                    {
                        items.map(item =>
                            <li key={item.id}>{item.name}</li>
                        )
                    }
                    </ul>
                </React.Fragment>
            );
        }
    }

This should work if result.items is an array.