how to deep copy object in javascript

let a = { x: 10, y: 15 };
let b = Object.assign({}, a);
console.log(a);
//output: { x: 10, y: 15 }
console.log(b);
//output: { x: 10, y: 15 }
console.log(a === b);
//output: false

const obj1 = { a: 1, b: 2, c: 3 };
// this converts the object to string so there will be no reference from 
// this first object
const s = JSON.stringify(obj1);

const obj2 = JSON.parse(s);

//recursive deep copy of object
function dup(o) {
    // "string", number, boolean
    if(typeof(o) != "object") {
        return o;
    }
    
     // null
    if(!o) {
        return o; // null
    }
    
    var r = (o instanceof Array) ? [] : {};
    for(var i in o) {
        if(o.hasOwnProperty(i)) {
            r[i] = dup(o[i]);
        }
    }
    return r;
}