Cloning an Object in Node js

Question

What is the best way to clone an object in node js  e g  I want to avoid the situation where   var obj1    x  5  y 5   var obj2   obj1  obj2 x   6  console log obj1 x      logs 6   The object may well contain complex types as attributes  so a simple for var x in obj1  wouldn t solve   Do I need to write a recursive clone myself or is there something built in that I m not seeing

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Y all suffering yet the solution is simple   var obj1    x  5  y 5     var obj2       obj1      Boom

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You can also use SugarJS in NodeJS   http   sugarjs com   They have a very clean clone feature  http   sugarjs com api Object clone

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There is another library lodash  it has clone and cloneDeep  clone will clone your object but not create a new instance for non-primitive values  instead it will use the referrence to the original object cloneDeep will create literally new objects without having any referrence to the original object  so it more safe when you have to change the object afterwards

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There are some Node modules out there if don t want to  roll your own   This one looks good  https   www npmjs com package clone  Looks like it handles all kinds of stuff  including circular references  From the github page      clone masters cloning objects  arrays  Date objects  and RegEx   objects  Everything is cloned recursively  so that you can clone dates   in arrays in objects  for example        Circular references  Yep

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Object defineProperty Object prototype   extend         enumerable  false      value  function from            var props   Object getOwnPropertyNames from           var dest   this          props forEach function name                if  name in dest                    var destination   Object getOwnPropertyDescriptor from  name                   Object defineProperty dest  name  destination                                     return this              This will define an extend method that you can use  Code comes from this article

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You can use the extend function from JQuery   var newClone  jQuery extend     oldObject     var deepClone   jQuery extend true      oldObject      There is a Node js Plugin too   https   github com shimondoodkin nodejs-clone-extend  To do it without JQuery or Plugin read this here   http   my opera com GreyWyvern blog show dml 1725165

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Check out underscore js  It has both clone and extend and many other very useful functions   This can be useful  Using the Underscore module with Node js

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There is also a project on Github that aims to be a more direct port of the jQuery extend     https   github com dreamerslab node extend  An example  modified from the jQuery docs   var extend   require  node extend     var object1         apple  0      banana            weight  52          price  100            cherry  97     var object2         banana            price  200            durian  100     var merged   extend object1  object2

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None of the answers satisfied me  several don t work or are just shallow clones  answers from  clint-harris and using JSON parse stringify are good but quite slow  I found a module that does deep cloning fast  https   github com AlexeyKupershtokh node-v8-clone

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Looking for a true clone option  I stumbled across ridcully s link to here   http   my opera com GreyWyvern blog show dml 1725165  I modified the solution on that page so that the function attached to the Object prototype is not enumerable   Here is my result   Object defineProperty Object prototype   clone         enumerable  false      value  function             var newObj    this instanceof Array                     for  i in this            if  i     clone   continue              if  this i   amp  amp  typeof this i      object                     newObj i    this i  clone                  else newObj i    this i            return newObj              Hopefully this helps someone else as well   Note that there are some caveats    particularly with properties named  clone    This works well for me   I don t take any credit for writing it   Again  I only changed how it was being defined

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You can prototype object and then call object instance every time you want to use and change object   function object        this x   5    this y   5    var obj1   new object    var obj2   new object    obj2 x   6  console log obj1 x     logs 5   You can also pass arguments to object constructor  function object  x  y       this x   x     this y   y    var obj1   new object 5  5   var obj2   new object 6  6   console log obj1 x     logs 5 console log obj2 x     logs 6   Hope this is helpful

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Possibility 1 Low-frills deep copy  var obj2   JSON parse JSON stringify obj1     Possibility 2  deprecated  Attention  This solution is now marked as deprecated in the documentation of Node js   The util  extend   method was never intended to be used outside of internal Node js modules  The community found and used it anyway  It is deprecated and should not be used in new code  JavaScript comes with very similar built-in functionality through Object assign     Original answer   For a shallow copy  use Node s built-in util  extend   function  var extend   require  util    extend   var obj1    x  5  y 5   var obj2   extend     obj1   obj2 x   6  console log obj1 x      still logs 5  Source code of Node s  extend function is in here  https   github com joyent node blob master lib util js exports  extend   function origin  add         Don t do anything if add isn t an object   if   add    typeof add      object   return origin     var keys   Object keys add     var i   keys length    while  i--        origin keys i     add keys i          return origin

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npm install node-v8-clone   Fastest cloner  it open native clone method from node js  var clone   require  node-v8-clone   clone  var newObj   clone obj  true     true - deep recursive clone

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There is no built-in way to do a real clone  deep copy  of an object in node js  There are some tricky edge cases so you should definitely use a library for this  I wrote such a function for my simpleoo library  You can use the deepCopy function without using anything else from the library  which is quite small  if you don t need it  This function supports cloning multiple data types  including arrays  dates  and regular expressions  it supports recursive references  and it also works with objects whose constructor functions have required parameters   Here is the code     If Object create isn t already defined  we just do the simple shim  without the second argument    since that s all we need here var object create   Object create  if  typeof object create      function         object create   function o            function F              F prototype   o          return new F                     Deep copy an object  make copies of all its object properties  sub-properties  etc      An improved version of http   keithdevens com weblog archive 2007 Jun 07 javascript clone    that doesn t break if the constructor has required parameters        It also borrows some code from http   stackoverflow com a 11621004 560114      function deepCopy   function deepCopy src     INTERNAL     visited        if src    null    typeof src       object            return src                Initialize the visited objects array if needed        This is used to detect cyclic references     if   visited    undefined            visited                    Ensure src has not already been visited     else           var i  len    visited length          for  i   0  i  lt  len  i                     If src was already visited  don t try to copy it  just return the reference             if  src      visited i                     return src                                        Add this object to the visited array      visited push src          Honor native custom clone methods     if typeof src clone     function            return src clone true                Special cases        Array     if  Object prototype toString call src       object Array                   slice 0  would soft clone         ret   src slice            var i   ret length          while  i--               ret i    deepCopy ret i    visited                     return ret              Date     if  src instanceof Date            return new Date src getTime                 RegExp     if  src instanceof RegExp            return new RegExp src               DOM Element     if  src nodeType  amp  amp  typeof src cloneNode     function             return src cloneNode true                If we ve reached here  we have a regular object  array  or function        make sure the returned object has the same prototype as the original     var proto    Object getPrototypeOf   Object getPrototypeOf src   src   proto         if   proto            proto   src constructor prototype    this line would probably only be reached by very old browsers            var ret   object create proto        for var key in src             Note  this does NOT preserve ES5 property attributes like  writable    enumerable   etc            For an example of how this could be modified to do so  see the singleMixin   function         ret key    deepCopy src key    visited             return ret

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I m surprised Object assign hasn t been mentioned   let cloned   Object assign     source     If available  e g  Babel   you can use the object spread operator   let cloned         source

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If you re using coffee-script  it s as easy as   newObject      newObject key    value  for own key value of oldObject   Though this isn t a deep clone

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Simple and the fastest way to clone an Object in NodeJS is to use Object keys  obj   method  var a     a    a11    b    avc    var b   for var keys   Object keys a   l   keys length  l  --l       b  keys l-1      a  keys l-1       b a   0   console log  a      JSON stringify a       LOG  a    a   a11   b   avc    console log  b      JSON stringify b       LOG  b    a  0  b   avc     The method Object keys requires JavaScript 1 8 5  nodeJS v0 4 11 supports this method  but of course for nested objects need to implement recursive func    Other solution is to use native JSON  Implemented in JavaScript 1 7   but it s much slower   10 times slower  than previous one  var a     a   i   b   i i   var b   JSON parse JSON stringify a    b a   0

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var obj2   JSON parse JSON stringify obj1

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This code is also work cause The Object create   method creates a new object with the specified prototype object and properties      var obj1    x 5  y 5    var obj2   Object create obj1    obj2 x    5 obj2 x   6  obj2 x    6  obj1 x    5

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Another solution is to encapsulate directly in the new variable using   obj1      obj2

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You can also use this clone library to deep clone objects    npm install --save clone   const clone   require  clone     const clonedObject   clone sourceObject

[javascript] Cloning an Object in Node.js

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