Filtering an array of objects based on another array of objects in javascript

Question

I have an array of messages like

oldMessages = [ {id:1,message:'message_A'} , {id:2,message:'message_B'} ]

and another array as

newMessages = [ {id:1,message:'message_A'} , {id:2,message:'message_B'} , {id:3,message:'message_C'} ]

How do I get only the part {id:3,message:'message_c'} by comparing oldMessages with newMessages? I must compare them based on their id only.

Hi and welcome. Can you post some code of what have you tried, please? — Dani
– Dani, Commented Jun 2, 2020 at 15:25
I wanted to, but my code is messed up, so I posted above example, any help on it is very much appreciated, thank you — Kritish Bhattarai
– Kritish Bhattarai, Commented Jun 2, 2020 at 15:29

palaѕн · Accepted Answer · 2020-06-02 15:30:02Z

1

You can easily do this using array .find() method like:

const oldMessages = [ {id:1,message:'message_A'} , {id:2,message:'message_B'} ]
const newMessages = [ {id:1,message:'message_A'},{id:2,message:'message_B'} , {id:3,message:'message_C'} ]
const data = newMessages.find(r=> !oldMessages.map(x=>x.id).includes(r.id))

console.log( data )

answered Jun 2, 2020 at 15:30

palaѕн

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