How can i get object with highest value?

I have this nested objects

var obj = {
    first:{
        num:10
    },
    second: {
        num:5
    },
    third: {
        num: 15
    }
}

console.log(obj);

so there could be a lot of nested objects inside and i need to get the object with highest num value inside which in this case is the third object.

So i should get as output

third: {
        num: 15
 }

I got stuck at the iteration

var arr = Object.keys( obj ).map(function ( key, index ) { 
    console.log(obj[key]);
 });
console.log(arr);

If you want the whole object back with the high value, I would use reduce

var obj = {
    first:{
        num:10
    },
    second: {
        num:5
    },
    third: {
        num: 15
    }
}

const result = Object.entries(obj)
                     .reduce( (acc,[k,i]) => Object.values(acc)[0].num<i.num ? {[k]:i} : acc
                                             , {zero:{num:0}})

console.log(result);

as I mentioned in my comment above, what you mentioned as expected output is not really an object. however, you can use following snippet to find the key within ur main object which holds the highest num:

var running = Number.MIN_VALUE;
var ans = "";
Object.keys(object).forEach(key => {
    if(object[key]["num"] > running) {
        ans = key;
    }
})
console.log(JSON.stringify(object[ans])); //outputs { num: 15 }