JSON find in JavaScript

Question

Is there a better way other than looping to find data in JSON  It s for edit and delete   for var k in objJsonResp      if  objJsonResp k  txtId    id        if  action     delete           objJsonResp splice k 1         else         objJsonResp k    newVal            break          The data is arranged as list of maps  Like        id value  pId value  cId value          id value  pId value  cId value

User · Answer

Zapping - you can use this javascript lib; DefiantJS. There is no need to restructure JSON data into objects to ease searching. Instead, you can search the JSON structure with an XPath expression like this:

    var data = [
   {
      "id": "one",
      "pId": "foo1",
      "cId": "bar1"
   },
   {
      "id": "two",
      "pId": "foo2",
      "cId": "bar2"
   },
   {
      "id": "three",
      "pId": "foo3",
      "cId": "bar3"
   }
],
res = JSON.search( data, '//*[id="one"]' );

console.log( res[0].cId );
// 'bar1'

DefiantJS extends the global object JSON with a new method; "search" which returns array with the matches (empty array if none were found). You can try it out yourself by pasting your JSON data and testing different XPath queries here:

http://www.defiantjs.com/#xpath_evaluator

XPath is, as you know, a standardised query language.

User · Answer

You re not searching through  JSON   you re searching through an array -- the JSON string has already been deserialized into an object graph  in this case an array    Some options   Use an Object Instead of an Array  If you re in control of the generation of this thing  does it have to be an array  Because if not  there s a much simpler way   Say this is your original data           id    one      pId    foo1    cId    bar1          id    two      pId    foo2    cId    bar2          id    three    pId    foo3    cId    bar3       Could you do the following instead          one       pId    foo1    cId    bar1         two       pId    foo2    cId    bar2         three     pId    foo3    cId    bar3       Then finding the relevant entry by ID is trivial   id    one      Or whatever var entry   objJsonResp id        as is updating it   objJsonResp id       New value          and removing it   delete objJsonResp id     This takes advantage of the fact that in JavaScript  you can index into an object using a property name as a string -- and that string can be a literal  or it can come from a variable as with id above   Putting in an ID-to-Index Map   Dumb idea  predates the above  Kept for historical reasons    It looks like you need this to be an array  in which case there isn t really a better way than searching through the array unless you want to put a map on it  which you could do if you have control of the generation of the object  E g   say you have this originally           id    one      pId    foo1    cId    bar1          id    two      pId    foo2    cId    bar2          id    three    pId    foo3    cId    bar3       The generating code could provide an id-to-index map          index              one   0   two   1   three   2             data               id    one      pId    foo1    cId    bar1              id    two      pId    foo2    cId    bar2              id    three    pId    foo3    cId    bar3             Then getting an entry for the id in the variable id is trivial   var index   objJsonResp index id   var obj   objJsonResp data index     This takes advantage of the fact you can index into objects using property names   Of course  if you do that  you have to update the map when you modify the array  which could become a maintenance problem   But if you re not in control of the generation of the object  or updating the map of ids-to-indexes is too much code and ora maintenance issue  then you ll have to do a brute force search   Brute Force Search  corrected   Somewhat OT  although you did ask if there was a better way  -     but your code for looping through an array is incorrect  Details here  but you can t use for  in to loop through array indexes  or rather  if you do  you have to take special pains to do so   for  in loops through the properties of an object  not the indexes of an array  Your best bet with a non-sparse array  and yours is non-sparse  is a standard old-fashioned loop   var k  for  k   0  k  lt  someArray length    k                  or  var k  for  k   someArray length - 1  k  gt   0  --k                  Whichever you prefer  the latter is not always faster in all implementations  which is counter-intuitive to me  but there we are    With a sparse array  you might use for  in but again taking special pains to avoid pitfalls  more in the article linked above    Using for  in on an array seems to work in simple cases because arrays have properties for each of their indexes  and their only other default properties  length and their methods  are marked as non-enumerable  But it breaks as soon as you set  or a framework sets  any other properties on the array object  which is perfectly valid  arrays are just objects with a bit of special handling around the length property

User · Answer

I had come across this issue for a complex model with several nested objects  A good example of what I was looking at doing would be this  Lets say you have a polaroid of yourself  And that picture is then put into a trunk of a car  The car is inside of a large crate  The crate is in the hold of a large ship with many other crates  I had to search the hold  look in the crates  check the trunk  and then look for an existing picture of me   I could not find any good solutions online to use  and using  filter   only works on arrays  Most solutions suggested just checking to see if model  yourpicture   existed  This was very undesirable because  from the example  that would only search the hold of the ship and I needed a way to get them from farther down the rabbit hole   This is the recursive solution I made  In comments  I confirmed from T J  Crowder that a recursive version would be required  I thought I would share it in case anyone came across a similar complex situation   function ContainsKeyValue  obj  key  value        if  obj key      value   return true      for  all in obj                 if  obj all     null  amp  amp  obj all  key      value                return true                    if  typeof obj all      object   amp  amp  obj all    null                var found   ContainsKeyValue  obj all   key  value                if  found    true   return true                      return false      This will start from a given object inside of the graph  and recurse down any objects found  I use it like this   var liveData       for  var items in viewmodel Crates         if  ContainsKeyValue  viewmodel Crates items    PictureId   6       true                 liveData push  viewmodel Crates items               Which will produce an array of the Crates which contained my picture

User · Answer

If you are doing this in more than one place in your application it would make sense to use a client-side JSON database because creating custom search functions is messy and less maintainable than the alternative   Check out ForerunnerDB which provides you with a very powerful client-side JSON database system and includes a very simple query language to help you do exactly what you are looking for      Create a new instance of ForerunnerDB and then ask for a database var fdb   new ForerunnerDB        db   fdb db  myTestDatabase        coll      Create our new collection  like a MySQL table  and change the default    primary key from   id  to  id  coll   db collection  myCollection    primaryKey   id         Insert our records into the collection coll insert         name   my Name   id  12  type   car owner          name   my Name2   id  13  type   car owner2          name   my Name4   id  14  type   car owner3          name   my Name4   id  15  type   car owner5           Search the collection for the string  my nam  as a case insensitive    regular expression - this search will match all records because every    name field has the text  my Nam  in it var searchResultArray   coll find       name   my nam i      console log searchResultArray       Outputs         name   my Name   id  12  type   car owner          name   my Name2   id  13  type   car owner2          name   my Name4   id  14  type   car owner3          name   my Name4   id  15  type   car owner5          Disclaimer  I am the developer of ForerunnerDB

User · Answer

If the JSON data in your array is sorted in some way  there are a variety of searches you could implement  However  if you re not dealing with a lot of data then you re probably going to be fine with an O n  operation here  as you have   Anything else would probably be overkill

User · Answer

General Solution We use object-scan for a lot of data processing  It has some nice properties  especially traversing in delete safe order  Here is how one could implement find  delete and replace for your question   x000D   x000D     const objectScan   require  object-scan     const tool         gt      const scanner   objectScan                abort  true      rtn   bool       filterFn           value  parent  property  context          gt          if  value id     context id            context fn   value  parent  property             return true                return false                return       add   data  id  obj    gt  scanner data    id  fn     parent  property      gt  parent splice property   1  0  obj          del   data  id    gt  scanner data    id  fn     parent  property      gt  parent splice property  1          mod   data  id  prop  v   undefined    gt  scanner data          id        fn     value      gt            if  value     undefined              value prop    v            else             delete value prop                                           -------------------------------  const data       id   one   pId   foo1   cId   bar1       id   three   pId   foo3   cId   bar3       const toAdd     id   two   pId   foo2   cId   bar2      const exec    fn    gt      console log  ---------------      console log fn toString       console log fn       console log data       exec      gt  tool add data   one   toAdd    exec      gt  tool mod data   one    pId    zzz     exec      gt  tool mod data   one    other    test     exec      gt  tool mod data   one    gone    delete me     exec      gt  tool mod data   one    gone     exec      gt  tool del data   three           gt  ---------------      gt       gt  tool add data   one   toAdd       gt  true      gt      id   one   pId   foo1   cId   bar1       id   two   pId   foo2   cId   bar2       id   three   pId   foo3   cId   bar3           gt  ---------------      gt       gt  tool mod data   one    pId    zzz        gt  true      gt      id   one   pId   zzz   cId   bar1       id   two   pId   foo2   cId   bar2       id   three   pId   foo3   cId   bar3           gt  ---------------      gt       gt  tool mod data   one    other    test        gt  true      gt      id   one   pId   zzz   cId   bar1   other   test       id   two   pId   foo2   cId   bar2       id   three   pId   foo3   cId   bar3           gt  ---------------      gt       gt  tool mod data   one    gone    delete me        gt  true      gt      id   one   pId   zzz   cId   bar1   other   test   gone   delete me       id   two   pId   foo2   cId   bar2       id   three   pId   foo3   cId   bar3           gt  ---------------      gt       gt  tool mod data   one    gone        gt  true      gt      id   one   pId   zzz   cId   bar1   other   test   gone  undefined      id   two   pId   foo2   cId   bar2       id   three   pId   foo3   cId   bar3           gt  ---------------      gt       gt  tool del data   three        gt  true      gt      id   one   pId   zzz   cId   bar1   other   test   gone  undefined      id   two   pId   foo2   cId   bar2      x000D   as-console-wrapper  max-height  100   important  top  0  x000D   lt script src  https   bundle run object-scan 13 7 1  gt  lt  script gt  x000D   x000D   x000D   Disclaimer  I m the author of object-scan

User · Answer

Ok  So  I know this is an old post  but perhaps this can help someone else   This is not backwards compatible  but that s almost irrelevant since Internet Explorer is being made redundant  Easiest way to do exactly what is wanted  function findInJson objJsonResp  key  value  aType                if aType   quot edit quot            return objJsonResp find x  gt  x key     value         else   delete          var a  objJsonResp find x  gt  x key     value            objJsonResp splice objJsonResp indexOf a  1             It will return the item you want to edit if you supply  edit  as the type  Supply anything else  or nothing  and it assumes delete  You can flip the conditionals if you d prefer

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