CODEWITHSUNDEEP
javascriptnode.jssocket.io
Vytautas Butkus
Vytautas Butkus

Reputation: 5535

Socket.io "on" function - pass additional parameters

I can't find a nice way to pass additional parameters to socket.io 'on' handler, i.e.:

var someEventHandler = require('someEventHandler'),
    additionalData = {test: 1};
socket.on('event', someEventHandler);

Now I want to access additionalData object inside someEventHandler function which is located in another file. Is there a similar way to pass arguments to handlers like jQuery 'on' gives us? ( $obj.on('event', '.selector', dataObject, handlerFunction) )

Upvotes: 3

Views: 2806

Answers (2)

Telokis
Telokis

Reputation: 3389

Since you don't like wrapping the callback yourself, you can change the socket.on function to make it match your desires. Something like 

const originalOn = socket.on;
socket.on = function (event, data, callback) {
    return originalOn.call(socket, event, (e) => callback(e, data));
};

You can now use it like so:

let data = {/* important data */};
socket.on('importantEvent', data, (e, additionalData) => {
    // Have fun with your data
});

Upvotes: 1

Brad Peabody
Brad Peabody

Reputation: 11397

You can use another function to handle the event, which then passes whatever additional data you need. Example:

var someEventHandler = require('someEventHandler'),
    additionalData = {test: 1};
socket.on('event', function(e) { someEventHandler(e, additionalData); } );

Upvotes: 4

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