javascript - 使用 create-react-app 获取 api 数据

Question

我是 reactjs 的新手，我正在使用 create-react-app 开始，但我不明白如何进行 api 调用来获取数据。这是我的代码：

import React, { Component } from 'react';
import logo from './logo.svg';
import './App.css';
// import { URL, KEY, city, countryCode } from './config.json';


const KEY = "d7ba7d7818dd3cec9ace78f9ad55722e";
const URL = "api.openweathermap.org/data/2.5";
const CITY = "Paris";

class App extends Component {
  constructor(props) {
    super(props);
    this.state = {
      data: {}
    };
  }

  componentDidMount() {
    var url = `${URL}/weather?q=${CITY}&APPID=${KEY}&units=metric`;
    console.log(url);
    fetch(url).then(
      response => response.json()
    ).then(
      json => {
        console.log(json);
        this.setState({data: json});
      }
    );
  }

  render() {
    return (
      <div className="App">
        <header className="App-header">
          <img src={logo} className="App-logo" alt="logo" />
          <h1 className="App-title">Welcome to React</h1>
        </header>
        <p className="App-intro">
          To get started, edit <code>src/App.js</code> and save to reload.
        </p>
      </div>
    );
  }
}

export default App;

render 方法只是 create-react-app 的默认渲染，我没有更改它。我只添加了构造函数和 componentDidMount 方法。我尝试从 OpenWeatherMap API 获取一些数据，将其添加到状态并将其记录到控制台。

该请求在邮递员中完美运行，但在我的应用程序中引发了此错误： SyntaxError: JSON.parse: unexpected character at line 1 column 1 of the JSON data

谁能帮我 ？

标签： javascriptreactjsfetchcreate-react-app

Answer 1

在 URL 中包含协议以解决问题。获取请求的响应不成功，因此当您尝试将响应解析为 JSON 时，它会抛出异常，因为响应它不是有效的 JSON。

const KEY = "d7ba7d7818dd3cec9ace78f9ad55722e";
// Made change here
const URL = "https://api.openweathermap.org/data/2.5";
const CITY = "Paris";

class App extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      data: {}
    };
  }

  componentDidMount() {
    var url = `${URL}/weather?q=${CITY}&APPID=${KEY}&units=metric`;
    console.log(url);
    fetch(url).then(
      response => response.json()
    ).then(
      json => {
        console.log(json);
        this.setState({data: json});
      }
    ).catch(error => console.log(error));
  }

  render() {
    return (
      <div className="App">
        <header className="App-header">
          <h1 className="App-title">Welcome to React</h1>
        </header>
        <p className="App-intro">
          To get started, edit <code>src/App.js</code> and save to reload.
        </p>
      </div>
    );
  }
}

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

<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="example"></div>