javascript - How to only transmit data through websocket if different from previous transmission -

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i have built simple web application using nodejs + express, request , socket.io modules json data external api , transmit using websocket client.

what transmit through websocket if externally requested json data has changed.

i cannot figure out how add condition code have come far:

io.on('connection', function (socket) {  setinterval(function () {   request({    url: url,    json: true   }, function (error, response, body) {    var senddata = json.stringify(body.result).tolowercase();    if (!error && response.statuscode === 200) {     socket.emit('result', senddata);    }   })  }, 3000) });

you can store last data each socket in object, compare senddata:

var lastdata = {};  //declare object io.on('connection', function (socket) {  setinterval(function () {   request({    url: url,    json: true   }, function (error, response, body) {    var senddata = json.stringify(body.result).tolowercase();    if (!error && response.statuscode === 200) {     if (senddata !== lastdata[socket.id]) {  //compare senddata last data      lastdata[socket.id] = senddata;   //store new last data      socket.emit('result', senddata);     }    }   })  }, 3000) });

hope helps.


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