arrays - Javascript - Deep copy specific properties from one object to another new object -

suppose have source object can arbitrary javascript object, may have properties objects (or arrays or functions), nested level.

i want perform deep copy of object new target object. want copy specific white-listed properties. these @ level in source object.

up till i've been manually assigning white-listed properties in source object target object. doesn't seem elegant , nor reusable. can please give me guidance on implementing using more elegant , re-usable approach?

this should looking for, including circular references.

edit: keep in mind slower , slower objects lots of circular references inside! lookup see if reference has been seen simple scan.

var util = require('util')   var propertiestocopy = {     'a' : true,     'b' : true,     'c' : true,     'd' : true,     'e' : true,     'f' : true,     'p1': true,     'p2': true,     'g' : true };  var obj;  obj = {     p2 : {          : 1,         b : 2,         c : {},         d : {             f : 2         }     },     p3 : 'hello' };  // circular obj.p1 = obj; obj.p2.d.e = obj;  // sub-circular obj.p2.g = obj.p2.c;  function getnewobjectfromobjects(obj, objects) {     (var = 0; < objects.length; i++) {         if (obj === objects[i].old) return  objects[i].new;     }     return false; }  function whitelistedcopy(obj, whitelist, root, newroot, objects) {     var cloned = {};     var keys = object.keys(obj);     root = root || obj;     newroot = newroot || cloned;     objects = objects || [ {'old' : root, 'new': newroot} ];     keys.foreach(function(val) {         if (whitelist[val] === true) {             if (typeof(obj[val]) === typeof({}) ||                  typeof(obj[val]) === typeof([]) ) {                 var reference = getnewobjectfromobjects(obj[val], objects);                 if (reference === false) {                 cloned[val] = whitelistedcopy(obj[val], whitelist, root, newroot, objects);                                                              objects.push({ 'old' : obj[val], 'new': cloned[val]});                 } else {                     cloned[val] = reference;                 }             } else {                 cloned[val] = obj[val];             }         }     });     return cloned; }  var clonedobject = whitelistedcopy(obj, propertiestocopy);  console.log(util.inspect(clonedobject));  console.log('assert c , g same reference:', clonedobject.p2.g === clonedobject.p2.c); console.log('assert p1 circular:', clonedobject === clonedobject.p1);