Javascript objects get parent

Question

I have the following  nested  object   obj    subObj    foo   hello world         Next thing I do is to reference the subobject like this   var s   obj subObj    Now what I would like to do is to get a reference to the object obj out of the variable s  Something like   var o   s parent    Is this somehow possible

User · Accepted Answer

No   There is no way of knowing which object it came from   s and obj subObj both simply have references to the same object   You could also do   var obj     subObj   foo   hello world      var obj2       obj2 subObj   obj subObj  var s   obj subObj    You now have three references  obj subObj  obj2 subObj  and s  to the same object   None of them is special

User · Answer

Try this until a non-no answer appears   function parent       this child    interestingProperty    5            function child       this parent           a   new parent    a child   new child    a child parent   a     this gives the child a reference to its parent  alert a interestingProperty         a child parent interestingProperty

User · Answer

This is an old question but as I came across it looking for an answer I thought I will add my answer to this to help others as soon as they got the same problem   I have a structure like this   var structure          root             name   Main Level           nodes                node1                     name   Node 1                                node2                     name   Node 2                                node3                     name   Node 3                                      Currently  by referencing one of the sub nodes I don t know how to get the parent node with it s name value  Main Level    Now I introduce a recursive function that travels the structure and adds a parent attribute to each node object and fills it with its parent like so   var setParent   function o        if o nodes    undefined             for n in o nodes                 o nodes n  parent   o                setParent o nodes n                           Then I just call that function and can now get the parent of the current node in this object tree   setParent structure root     If I now have a reference to the seconds sub node of root  I can just call   var node2   structure root nodes  node2    console log node2 parent name     and it will output  Main Level    Hope this helps

User · Answer

I have been working on a solution to finding the parent object of the current object for my own pet project  Adding a reference to the parent object within the current object creates a cyclic relationship between the two objects   Consider -   var obj         innerObj          setParent  function            this innerObj parent   this           obj setParent      The variable obj will now look like this -  obj innerObj parent innerObj parent innerObj     This is not good  The only solution that I have found so far is to create a function which iterates over all the properties of the outermost Object until a match is found for the current Object and then that Object is returned     Example -  var obj         innerObj            innerInnerObj               var o   obj innerObj innerInnerObj      found   false   var getParent   function  currObj  parObj        for var x in parObj           if parObj hasOwnProperty x                if parObj x      currObj                   found   parObj               else if typeof parObj x       object                    getParent currObj  parObj x                                      return found      var res   getParent o  obj      res   obj innerObj   Of course  without knowing or having a reference to the outermost object  there is no way to do this  This is not a practical nor is it an efficient solution  I am going to continue to work on this and hopefully find a good answer for this problem

User · Answer

Many of the answers here involve looping through an object and  manually   albeit programmatically  creating a parent property that stores the reference to the parent  The two ways of implementing this seem to be      Use an init function to loop through at the time the nested object is created  or    Supply the nested object to a function that fills out the parent property   Both approaches have the same issue     How do you maintain parents as the nested object grows changes    If I add a new sub-sub-object  how does it get its parent property filled  If you re  1  using an init function  the initialization is already done and over  so you d have to  2  pass the object through a function to search for new children and add the appropriate parent property   Using ES6 Proxy to add parent whenever an object sub-object is set  The approach below is to create a handler for a proxy always adds a parent property each time an object is set  I ve called this handler the parenter handler  The parenter responsibilities are to recognize when an object is being set and then to      Create a dummy proxy with the appropriate parent and the parenter handler  var p   new Proxy  parent  target   parenter    Copy in the supplied objects properties-- Because you re setting the proxy properties in this loop the parenter handler is working recursively  nested objects are given parents at each level  for key in value       p key    value key        Set the proxy not the supplied object  return target prop    p     Full code  var parenter       set  function target  prop  value       if typeof value      object          var p   new Proxy  parent  target   parenter         for key in value           p key    value key                 return target prop    p       else        target prop    value               var root   new Proxy     parenter       some examples root child1         color   red        value  10       otherObj            otherColor   blue           otherValue  20             parents exist behave as expected console log root child1 color                      red  console log root child1 otherObj parent color      red      new children automatically have correct parent root child2    color   green   value3  50   console log root child2 parent child1 color        red      changes are detected throughout root child1 color    yellow  console log root child2 parent child1 color        yellow    Notice that all root children always have parent properties  even children that are added later

User · Answer

Just in keeping the parent value in child attribute  var Foo   function        this val  4      this test         this test val 6      this test par this     var myObj   new Foo    alert myObj val   alert myObj test val   alert myObj test par val

User · Answer

You will need the child to store the parents this variable  As the Parent is the only object that has access to it s this variable it will also need a function that places the this variable into the child s that variable  something like this   var Parent       Child         that              init   function        this Child that   this          To test this out try to run this in Firefox s Scratchpad  it worked for me   var Parent       data    Parent Data      Child         that           data    Child Data       display   function          console log this data         console log this that data                init   function        this Child that   this         Parent init    Parent Child display

User · Answer

There is a more  smooth  solution for this     var Foo   function      this par   3     this sub   new function t     using virtual function to create sub object and pass parent object via  t      this p   t      this subFunction   function          alert this p par              this      var myObj   new Foo    myObj sub subFunction      will popup 3   myObj par   5  myObj sub subFunction      will popup 5

User · Answer

To further iterate on Mik s answer  you could also recursivey attach a parent to all nested objects   var myApp          init  function             for  var i in this                if  typeof this i      object                         this i  init   this init                      this i  init                        this i  parent   this                                  return this              obj1            obj2                notify  function                     console log this parent parent obj3 msg                                       obj3            msg   Hello           init     myApp obj1 obj2 notify      http   jsbin com zupepelaciya 1 watch js console

User · Answer

You could try this this uses a constructor  but I m sure you can change it around a bit    function Obj         this subObj                code           this subObj parent   this

User · Answer

when I load in a json object I usually setup the relationships by iterating through the object arrays like this       for  var i   0  i  lt  some json objectarray length  i              var p   some json objectarray i           for  var j   0  j  lt  p somechildarray length  j                  p somechildarray j  parent   p                    then you can access the parent object of some object in the somechildarray by using  parent

User · Answer

A nested object  child  inside another object  parent  cannot get data directly from its parent     Have a look on this     var main         name    main object       child             name    child object             If you ask the main object what its child name is  main child name  you will get it  Instead you cannot do it vice versa because the child doesn t know who its parent is   You can get main name but you won t get main child parent name      By the way  a function could be useful to solve this clue  Let s extend the code above     var main         name    main object       child             name    child object             init   function             this child parent   this          delete this init          return this          init      Inside the init function you can get the parent object simply calling this  So we define the parent property directly inside the child object  Then  optionally  we can remove the init method  Finally we give the main object back as output from the init function     If you try to get main child parent name now you will get it right  It is a little bit tricky but it works fine

[javascript] Javascript objects: get parent

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