问来自客户端javascript的错误400认知/OAuth2/令牌端点

EN

const XHR = new XMLHttpRequest();
    
let urlEncodedData = "",
    urlEncodedDataPairs = [],
    name;

urlEncodedDataPairs.push( encodeURIComponent( 'grant_type' ) + '=' + encodeURIComponent( 'authorization_code' ) );
urlEncodedDataPairs.push( encodeURIComponent( 'code' ) + '=' + encodeURIComponent( code ) );
urlEncodedDataPairs.push( encodeURIComponent( 'client_id' ) + '=' + encodeURIComponent( 'xxxxx' ) );
urlEncodedDataPairs.push( encodeURIComponent( 'redirect_url' ) + '=' + encodeURIComponent( 'https://www.xxx.me/xxx' ) );
    
XHR.addEventListener( 'load', function(event) {
   alert( 'Yeah! Data sent and response loaded.' );
} );
    
// Define what happens in case of error
XHR.addEventListener( 'error', function(event) {
    alert( 'Oops! Something went wrong.' );
});
    
// Set up our request
XHR.open( 'POST', 'https://xxx.auth.us-west-2.amazoncognito.com/oauth2/token' );
    
// Add the required HTTP header for form data POST requests
XHR.setRequestHeader( 'Content-Type', 'application/x-www-form-urlencoded' );
    
// Finally, send our data.
XHR.send( urlEncodedData );

   let tokenRequest = new Request(tokenURL, {
            method: 'POST',
            headers: {
                'Content-Type': 'application/x-www-form-urlencoded;charset=UTF-8',
                'Origin' : 'https://www.xxx.me'
            },
            body: new URLSearchParams({
                'grant_type': 'authorization_code',
                'code': code,
                'client_id': 'xxx',
                'redirect_url': 'https://www.xxx.me/xxx'
            }).toString()

        });

        let response = await fetch(tokenRequest);
        let data = await response.json();