How to find the same values ​​in two arrays of objects?

Question

JavaScript

Hello everyone, there are 2 arrays of objects, for example:
[{"id":1, "item": 213}]

[{"id":1, "item":  213}, {"id":78, "item":  21}, {"id":19, "item":  13}]

How to check if some object is in another array of objects? In this case, there must be one

Answer 1

var a = [{"id":1, "item": 213}];
var b = [{"id":1, "item":  213}, {"id":78, "item":  21}, {"id":19, "item":  13}];

var result = a.filter(function(v) {
    return b.some(function(v2) {
        return v.id == v2.id && v.item == v2.item;
    }
});
console.log(result);

Something like that. If you need more compatibility with older versions, tell me, I'll rewrite.

Answer 2

For two arrays of strings or numbers, the algorithm would be:
You can apply the algorithm, knowing the features of this particular problem. It is known that there are two fields, called id and item, their values ​​are integers. Let's make an array of pseudo-hashes from each, so that instead of an array of objects we deal with an array of strings.

function haveCommon(a,b) {
    var phash = function(e){ return '' + e.id + '.' + e.item }
       ,ha = a.map(phash).sort()
       ,hb = b.map(phash).sort()
       ,ia = 0
       ,ib = 0
    ;
    while( ia<ha.length  &&  ib<hb.length) {
        if( ha[ia] > hb[ib]) ib++;
        else if( ha[ia] < hb[ib]) ia++;
        else return true;
    }
    return false;
}

haveCommon( [{"id":1, "item": 213}]
    ,[{"id":1, "item":  213}, {"id":78, "item":  21}, {"id":19, "item":  13}]
) // true

Answer 3

or just connect lodash and use find/intersection