请求的资源上不存在 Access-Control-Allow-Origin header。 将请求的模式设置为 no-cors 以获取禁用 CORS 的资源

Question

has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled

The URL downloading a txt file in web browser https://google.com/complete/search?client=chrome&q=python

import './App.css';
import {useState} from 'react';

function App() {
  const [Keyword, setKeyword] = useState("");
  const [Result, setResult] = useState([]);

  const findMatch = async () => {
    const getMatch = await fetch("http://google.com/complete/search?client=chrome&q=" + Keyword, {
      method: 'GET',
      headers: {
      'Access-Control-Allow-Origin': true,
      'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/70.0.3538.102 Safari/537.36 Edge/18.19582',
      'Content-Type': 'text/plain',
      },
    })
    console.log(getMatch);
  }

  return (
    <div className="App">
      <input placeholder='Put Keyword' value={Keyword} onChange={(e) => setKeyword(e.target.value)} />
      <button onClick={findMatch}>Search</button>
    </div>
  );
}

export default App;

Answer 1

CORS is a server-side origin checking service where you can allow or disallow certain origins to request your resources. Given this, your header option 'Access-Control-Allow-Origin': true would be returned from the server in a RESPONSE header, while you're trying to put it in the REQUEST header and this will not work. You can try disabling CORS on your request, although this will allow for less headers in your request:

const getMatch = await fetch("http://google.com/complete/search?client=chrome&q=" + Keyword, {
      method: 'GET',
      mode: 'no-cors',
      headers: {
      'Content-Type': 'text/plain',
      },
    })

Source: https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API/Using_Fetch#supplying_request_options

Answer 2

You can use a cors proxy service for that. for example, cors.sh