Can't send a Set() object via socket.io in node.js

Question

I'm trying to send a Set() object via socket.io from node.js server. But from client side I'm getting an empty object.

//server side
var set=new Set([1,2,3]);
socket.emit('set', set);
console.log(set); //Set(3) {1,2,3}

//client side
socket.on('set',function(set){
  console.log(set); //{}
});

Why is that ?

gurisko · Accepted Answer · 2020-09-30 11:37:22Z

6

From the docs:

All serializable datastructures are supported, including Buffer.

Set is not serializable (try doing JSON.stringify(new Set([1, 2, 3])). However, Array is serializable and you can convert a set into an array with a spread operator:

const s = new Set([1,2,3]);
socket.emit('set', [...s]);

edited Sep 30, 2020 at 11:37

answered Sep 30, 2020 at 9:07

gurisko

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2 Comments

Chamod Over a year ago

Thank you very much for the answer. Are there any performance difference between [...s] & Array.from(s)

gurisko Over a year ago

@Chamod It all depends on your environment - are you running natively or are you transpiling into ES5? Also, in most scenarios differences are going to be negligible. Have a look at Array.from() vs spread syntax

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