Selecting distinct values from a JSON

Question

I have my JSON as follows    DATA      id  11  name   ajax   subject   OR   mark  63     id  12  name   javascript   subject   OR   mark  63     id  13  name   jquery   subject   OR   mark  63     id  14  name   ajax   subject   OR   mark  63     id  15  name   jquery   subject   OR   mark  63     id  16  name   ajax   subject   OR   mark  63     id  20  name   ajax   subject   OR   mark  63    COUNT   120     Is there any good method to find out the distinct name from this JSON  Result javascript jquery ajax  I can do this using following methode   var arr       var j 0  for  var i   0  i  lt  varjson DATA length  i        if   inArray varjson DATA i   name   arr  lt 0         arr j  varjson DATA i   name          j            Is there any better method which gave me better performance

User · Answer

try this  MYJSON will be your json data   var mytky     mytky DistinctRecords MYJSON  mykeyname     function DistinctRecords MYJSON prop      return MYJSON filter  obj  pos  arr    gt        return arr map mapObj   gt  mapObj prop   indexOf obj prop       pos

User · Answer

First we can just run map   function to get the new array with the results of calling a provided function on every element in the varjson DATA   varjson DATA map   name    gt name     After getting the array of name from the varjson DATA  We can convert it into a set that will discard all duplicate entries of array and apply spread operator to get a array of unique names       new Set varjson DATA map   name    gt name       x000D   x000D  const varjson     x000D     DATA      x000D         id   11  x000D         name    ajax   x000D         subject    OR   x000D         mark   63 x000D         x000D        x000D         id   12  x000D         name    javascript   x000D         subject    OR   x000D         mark   63 x000D         x000D        x000D         id   13  x000D         name    jquery   x000D         subject    OR   x000D         mark   63 x000D         x000D        x000D         id   14  x000D         name    ajax   x000D         subject    OR   x000D         mark   63 x000D         x000D        x000D         id   15  x000D         name    jquery   x000D         subject    OR   x000D         mark   63 x000D         x000D        x000D         id   16  x000D         name    ajax   x000D         subject    OR   x000D         mark   63 x000D         x000D        x000D         id   20  x000D         name    ajax   x000D         subject    OR   x000D         mark   63 x000D        x000D       x000D     COUNT    120  x000D    x000D   x000D  console log      new Set varjson DATA map   name    gt name      x000D   x000D   x000D

User · Answer

Give this a go  var distinct list       data DATA map function  d   return d x     filter  v  i  a    gt  a indexOf v      i

User · Answer

As you can see here  when you have more values there is a better approach   http   jsfiddle net MsYGJ   temp         Store each of the elements in an object keyed of of the name field   If there is a collision  the name already exists  then it is just replaced with the most recent one  for  var i   0  i  lt  varjson DATA length  i          temp varjson DATA i  name    varjson DATA i        Reset the array in varjson varjson DATA          Push each of the values back into the array  for  var o in temp        varjson DATA push temp o        Here we are creating an object with the name as the key   The value is simply the original object from the array   Doing this  each replacement is O 1  and there is no need to check if it already exists   You then pull each of the values out and repopulate the array     NOTE For smaller arrays  your approach is slightly faster   NOTE 2 This will not preserve the original order

User · Answer

Use Jquery Method unique   var UniqueNames    unique data DATA map function  d   return d name       alert   unique names      JSFiddle

User · Answer

Underscore js is great for this kind of thing  You can use   countBy   to get the counts per name   data      id  11  name   ajax   subject   OR   mark  63             id  12  name   javascript   subject   OR   mark  63             id  13  name   jquery   subject   OR   mark  63             id  14  name   ajax   subject   OR   mark  63             id  15  name   jquery   subject   OR   mark  63             id  16  name   ajax   subject   OR   mark  63             id  20  name   ajax   subject   OR   mark  63      countBy data  function data    return data name        Gives    ajax  4  javascript  1  jquery  2     For an array of the keys just use   keys      keys   countBy data  function data    return data name         Gives     ajax    javascript    jquery

User · Answer

I would use one Object and one Array  if you want to save some cycle   var lookup       var items   json DATA  var result        for  var item  i   0  item   items i          var name   item name     if    name in lookup         lookup name    1      result push name           In this way you re basically avoiding the indexOf   inArray call  and you will get an Array that can be iterate quicker than iterating object s properties     also because in the second case you need to check hasOwnProperty   Of course if you re fine with just an Object you can avoid the check and the result push at all  and in case get the array using Object keys lookup   but it won t be faster than that

User · Answer

This is a great spot for a reduce  var uniqueArray   o DATA reduce function  a  d           if  a indexOf d name      -1             a push d name                   return a

[javascript] Selecting distinct values from a JSON

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