从websocket过滤json对象/值并打印到控制台日志

Question

尝试打印到控制台记录websocket提供的json数据中的值

下面的代码将所有json数据从websocket打印到控制台日志。

// require ws
const WebSocket = require('ws');


//messsage sent to  ws server
var msg = 
    {"jsonrpc": "2.0",
     "method": "public/subscribe",
     "id": 42,
     "params": {
        "channels": ["deribit_price_index.btc_usd"]}
    };

// WS connection url
var ws = new WebSocket('wss://test.deribit.com/ws/api/v2');

//ws response
ws.onmessage = function (e) {

    // do something with the notifications...

    console.log('server : ', e.data);

};

//stringify json data
ws.onopen = function () {
    ws.send(JSON.stringify(msg));
};

预期结果：

server :  5457.21

server :  5457.19

server :  5457.15

实际结果：

server :  {"jsonrpc":"2.0","method":"subscription","params":{"channel":"deribit_price_index.btc_usd","data":{"timestamp":1556209117657,"price":5457.21,"index_name":"btc_usd"}}}
server :  {"jsonrpc":"2.0","method":"subscription","params":{"channel":"deribit_price_index.btc_usd","data":{"timestamp":1556209117657,"price":5457.19,"index_name":"btc_usd"}}}

Answer 1

JSON.parse()

这是你如何使用它：

    //This will turn it into an object you can navigate with '.params.data.price'
    try {
        console.log('server: ', JSON.parse(e.data).params.data.price);
    } catch {}

Answer 2

您正在记录e.data中的所有内容。

根据实际结果json，看起来你想要e.data.params.data.price

正如Robofan所说，你需要先解析它。

console.log('server : ', e.data); - > console.log('server : ', JSON.parse(e).params.data.price);