节点服务器和Apache服务器 - 没有'访问控制 - 允许来源'错误

我有一个JS脚本运行，发送并尝试接收JSON数据。节点服务器和Apache服务器 - 没有'访问控制 - 允许来源'错误

此JS脚本运行在WAMP上，另一台服务器作为节点服务器运行。（节点服务器在localhost：3000上）。

当试图发送/接收数据，错误在控制台抛出：

的XMLHttpRequest无法加载http://localhost:3000/ ...回应预检要求未通过访问控制检查：没有“访问 - Control-Allow-Origin'标题出现在请求的资源上。因此不允许访问原产地'http://localhost'。

我的Javascript代码：

function sendHands(){ 
    console.log("sending hands"); 
    var xhr = new XMLHttpRequest(); 
    var params = getHandsFromDom(); 
    var hand1 = params[0]; 
    var hand2 = params[1]; 
    var url = "http://localhost:3000/?hand1="+hand1+"&"+"hand2="+hand2; 
    xhr.open("GET", url, true); 
    xhr.setRequestHeader("Content-type", "application/json"); 
    xhr.onreadystatechange = function() { 
     if (xhr.readyState === 4 && xhr.status === 200) { 
      var json = JSON.parse(xhr.responseText); 
      console.log("player1score: " + json.player1score); 
      document.getElementById("result").value = xhr.responseText; 
     } 
    }; 
    xhr.send(); 
}

节点服务器：

const requestHandler = (request, response) => { 
    var urlParts = url.parse(request.url, true), 
     urlParams = urlParts.query, //JSON hand data 
     body = ""; 

    // if the request is a GET request 
    if(request.method == 'GET'){ 
     response.writeHead(200, {'Content-Type':'application/json'}); 
     var body = ""; 
     var paramData = ""; 

     request.on('data' , function(data){ 
      body += data; 
     }); 
     process.on("uncaughtException", function(e){ 
      console.log("An error occurred: " + e); 
     }); 
     request.on("error", function(e){ 
      console.log("Error caught!"); 
     }); 

     request.on('end', function(){ 
      var hand1 = JSON.parse(urlParams.hand1), 
       hand2 = JSON.parse(urlParams.hand2), 
       hand3 = (urlParams.hand3 != null || urlParams.hand3 != undefined) 
          ? JSON.parse(urlParams.hand3) : null, 
      //process settlement of given hands 
       hands = _assocArrayGenerator(hand1, hand2, hand3), 
       settlement = pa.settlement(hands), 
       jsonSettlement = { 
        player1score : settlement[0], 
        player2score : settlement[1], 
        player3score : settlement[2] 
       }; 

      response.writeHead(200, {'Content-type':'application/json'}); 
      console.log("Server accessed. Result: " + settlement); 
      response.end(JSON.stringify(jsonSettlement)); 
     }); 
    } 
}; 

server.listen(port, (err) => { 
    if (err) { 
    return console.log('Error occured with the server: ', err); 
    } 

    console.log(`Server is listening on http://localhost:${port}`); 
})

难道这是为什么发生和给定的修补程序的工作怎么有人向我解释？

谢谢！

来源

2017-06-01 Joe McFarrlen