Clone Object without reference javascript

Question

I have a big object with much data  And i want to clone this in other variable  When i set some param of the instance B has the same result in the original object   var obj    a  25  b  50  c  75   var A   obj  var B   obj   A a   30  B a   40   alert obj a         A a         B a      40 40 40   My output should be 25 30 40  Any ideas   EDIT  Thanks Everyone  I change the code of dystroy and this is my result   Object prototype clone   Array prototype clone   function         if  Object prototype toString call this        object Array                  var clone               for  var i 0  i lt this length  i                clone i    this i  clone             return clone             else if  typeof this    object                 var clone               for  var prop in this              if  this hasOwnProperty prop                   clone prop    this prop  clone             return clone            else         return this     var obj    a  25  b  50  c  75   var A   obj clone    var B   obj clone    A a   30  B a   40  alert obj a         A a         B a    var arr    25  50  75   var C   arr clone    var D   arr clone    C 0    30  D 0    40  alert arr 0          C 0          D 0

User · Answer

You could define a clone function   I use this one    function goclone source        if  Object prototype toString call source        object Array              var clone               for  var i 0  i lt source length  i                  clone i    goclone source i                      return clone        else if  typeof source    object             var clone               for  var prop in source                if  source hasOwnProperty prop                     clone prop    goclone source prop                                    return clone        else           return source           var B   goclone A     It doesn t copy the prototype  functions  and so on  But you should adapt it  and maybe simplify it  for you own need

User · Answer

While this isn t cloning  one simple way to get your result is to use the original object as the prototype of a new one   You can do this using Object create   var obj    a  25  b  50  c  75   var A   Object create obj   var B   Object create obj    A a   30  B a   40   alert obj a         A a         B a      25 30 40   This creates a new object in A and B that inherits from obj  This means that you can add properties without affecting the original   To support legacy implementations  you can create a  partial  shim that will work for this simple task   if   Object create      Object create   function proto            function F             F prototype   proto          return new F          It doesn t emulate all the functionality  of Object create  but it ll fit your needs here

User · Answer

A and B reference the same object  so A a and B a reference the same property of the same object   Edit  Here s a  copy  function that may do the job  it can do both shallow and deep clones  Note the caveats  It copies all enumerable properties of an object  not inherited properties   including those with falsey values  I don t understand why other approaches ignore them   it also doesn t copy non   existent properties of sparse arrays    There is no general copy or clone function because there are many different ideas on what a copy or clone should do in every case  Most rule out host objects  or anything other than Objects or Arrays  This one also copies primitives  What should happen with functions   So have a look at the following  it s a slightly different approach to others      Only works for native objects  host objects are not    included  Copies Objects  Arrays  Functions and primitives     Any other type of object  Number  String  etc   will likely give     unexpected results  e g  copy new Number 5      gt  0 since the value    is stored in a non-enumerable property        Expects that objects have a properly set  constructor  property     function copy source  deep       var o  prop  type     if  typeof source     object     source     null           What do to with functions  throw an error      o   source      return o         o   new source constructor       for  prop in source         if  source hasOwnProperty prop           type   typeof source prop          if  deep  amp  amp  type     object   amp  amp  source prop      null            o prop    copy source prop             else           o prop    source prop                       return o

User · Answer

If you use an   statement to assign a value to a var with an object on the right side  javascript will not copy but reference the object   You can use lodash s clone method  var obj    a  25  b  50  c  75   var A     clone obj     Or lodash s cloneDeep method if your object has multiple object levels  var obj    a  25  b   a  1  b  2   c  75   var A     cloneDeep obj     Or lodash s merge method if you mean to extend the source object  var obj    a  25  b   a  1  b  2   c  75   var A     merge     obj   newkey   newvalue       Or you can use jQuerys extend method   var obj    a  25  b  50  c  75   var A     extend true    obj     Here is jQuery 1 11 extend method s source code    jQuery extend   jQuery fn extend   function         var src  copyIsArray  copy  name  options  clone          target   arguments 0                 i   1          length   arguments length          deep   false          Handle a deep copy situation     if   typeof target      boolean              deep   target              skip the boolean and the target         target   arguments  i                  i                  Handle case when target is a string or something  possible in deep copy      if   typeof target      object   amp  amp   jQuery isFunction target              target                     extend jQuery itself if only one argument is passed     if   i     length             target   this          i--             for     i  lt  length  i                  Only deal with non-null undefined values         if    options   arguments  i       null                    Extend the base object             for   name in options                     src   target  name                    copy   options  name                        Prevent never-ending loop                 if   target     copy                         continue                                        Recurse if we re merging plain objects or arrays                 if   deep  amp  amp  copy  amp  amp    jQuery isPlainObject copy      copyIsArray   jQuery isArray copy                             if   copyIsArray                             copyIsArray   false                          clone   src  amp  amp  jQuery isArray src    src                              else                           clone   src  amp  amp  jQuery isPlainObject src    src                                                     Never move original objects  clone them                     target  name     jQuery extend  deep  clone  copy                        Don t bring in undefined values                   else if   copy     undefined                         target  name     copy                                                          Return the modified object     return target

[javascript] Clone Object without reference javascript

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