update a Key wherever it present in given JSON

[SavinayaShetty]

Is it possible to update a key wherever it is present, irrespective of the structure of JSON?
In below example, I want to update the key "postback".
Example:
input:

{
  "menu": {
    "popup": {
      "menuitem": [
       {
          "action": "Open",
          "postback": "chose_open"
        },
        {
          "action": "Close",
          "postback": "chose_close"
        }
      ]
    },
   "option": {
         "action" : "OptOut",
         "postback": "not_intrested"
    }
  },
 "action": "more",
 "postback":"know_more"
}

output:

{
  "menu" : {
    "popup" : {
      "menuitem" : [ {
        "postback" : "USER1~chose_open",
        "action" : "Open"
      }, {
        "postback" : "USER1~chose_close",
        "action" : "Close"
      } ]
    },
    "option" : {
      "postback" : "USER1~not_intrested",
      "action" : "OptOut"
    }
  },
  "postback" : "USER1~know_more",
  "action" : "more"
}

jslt template used:

{
   "menu":{
      "popup":{
         "menuitem":[ for(.menu.popup.menuitem)
            {
               "postback":"USER1~"+.postback, 
               *:.
            }
         ]
      },
      "option":{
         "postback":"USER1~"+.menu.option.postback,
         *:.
      }
   },
   "postback":"USER1~"+.postback,
   *:.
}

Is there a more elegant way of doing this?
In the actual case, the USER1~ will be an external parameter I'll be passing to the template, and the input JSON will be more complex.
I'm fairly new to JSLT, just wondering if any feature is available to update all in one go instead of traversing.

[larsga]

This is an interesting feature suggestion, but I'm afraid there is no support for anything like this at the moment.

However, you can get what you want by writing a recursive traversal function that does the update on every object in the input. You can see some useful examples here https://github.com/schibsted/jslt/blob/master/tutorial.md#function-declarations

[larsga]

I see. You can do that by changing this part:

{for ($jsonObj)
        .key:

The .key there is an expression, so you can replace that with an if that returns the key name you want.

Of course, you also have to modify the rest of the function so that it doesn't replace the value.

[akashvekariya]

There exactly is a catch (or atleast I can't think of any solution to work). I want to know if I loop inside the object just like you saw, I'll need to put .key after the for loop condition so how can I check if the key matches and go back and rename or if it doesn't match with search parameter, return as it is.

Something like this I want to do, but apparently this is syntactically wrong.

def renameByKey(jsonObj, searchTerm, updatedKey)
   if (is-object($jsonObj))
      {for ($jsonObj)
        if ((is-object(.value) or is-array(.value)) and .key != $searchTerm)
           renameByKey(.value, $searchTerm, $updatedKey)
        else if (.key == $searchTerm)
           $updatedKey : .value
        else 
           .key : .value
      }
   else if (is-array($jsonObj))
      [for($jsonObj)
         renameByKey(., $searchTerm, $updatedKey)
      ]

[larsga]

Yes, the language just doesn't work that way. You're writing as if a : b is a value, but it's not. There are two values, separated by :.

It's like this:

{for ($jsonObj) 
  // here .key and .value are set
<expression to produce new key> : <expression to produce new value>
}

So what you need is the appropriate if on both sides of the :.

However, if you really want, you can make a [for ...] that produces [key, value] pairs, then pass that to a {for (...) .[0] : .[1]}. That will allow you to write the code that way you want.

[larsga]

This should do it:

def renameByKey(jsonObj, searchTerm, updatedKey)
   if (is-object($jsonObj))
      {for ($jsonObj)
        if (.key != $searchTerm) .key else $updatedKey
        :
        if ((is-object(.value) or is-array(.value)) and .key != $searchTerm)
           renameByKey(.value, $searchTerm, $updatedKey)
        else 
           .value
      }
   else if (is-array($jsonObj))
      [for($jsonObj)
         renameByKey(., $searchTerm, $updatedKey)
      ]
   else
      $jsonObj

[akashvekariya]

Hey, thanks man! exactly what I was looking for. Works just fine!