Elm Json Transform

This project provides a way to transform a json string. It uses Native javascript under the hood. For reasons of simplicity and usability it takes the json as a string and returns the modified json as a string. This is because that is what my use case for building this library was.

It uses js-traverse to traverse and modify JavaScript object nodes that match JSONSelect selectors.

Explorer

Try it out using the Elm Json Transform Explorer

Usage

There are 5 things you can do given the following json string:

{
   "george": {
      "age": 35,
      "movie": "Repo Man"
   },
   "mary": {
      "age": 15,
      "movie": "Twilight"
   }
}

forEach

Iterates over all matching nodes in the object. The callback gets a special this context. See js-traverse for all the things you can do to modify and inspect the node with this context. In addition, js-select adds a this.matches() which will test if the node matches a selector:

func = """
function(node) {
   if (this.matches(".mary > .movie")) {
      this.remove();
   }
}
"""

forEach obj func

returns:

{
   "george": {
      "age": 35,
      "movie": "Repo Man"
   },
   "mary": {
      "age": 15
   }
}

nodes

Returns all matching nodes from the object.

nodes obj ".age"

returns:

[35, 15]

remove

Removes matching elements from the original object.

remove obj ".age"

returns:

{
   "george": {
      "movie": "Repo Man"
   },
   "mary": {
      "movie": "Twilight"
   }
}

update

Updates all matching nodes using the given callback.

func = """
function(age) {
   return age - 5;
}
"""

update obj ".age" func

returns:

{
   "george": {
      "age": 30,
      "movie": "Repo Man"
   },
   "mary": {
      "age": 10,
      "movie": "Twilight"
   }
}

condense

Reduces the original object down to only the matching elements (the hierarchy is maintained).

condense obj ".age"

returns:

{
    george: { age: 35 },
    mary: { age: 15 }
}

updateObjectContaining

Updates key/value string pairs in an object that is located by a string key/value pair that exists inside the object

updateObjectContaining obj [("movie","Repo Man")] [("movie","Cars")]

returns:

{
   "george": {
      "age": 35,
      "movie": "Repo Man"
   },
   "mary": {
      "age": 15,
      "movie": "Cars"
   }
}

Selectors

it supports the following selectors:

*
type
.key
ancestor selector
parent > selector
sibling ~ selector
selector1, selector2
:root
:nth-child(n)
:nth-child(even)
:nth-child(odd)
:nth-last-child(n)
:first-child
:last-child
:only-child
:has(selector)
:val("string")
:contains("substring")

You can try them out using the JSONSelect expression tester

Install

you must use elm-github-install and include in your elm-package.json as follows:

"dependencies": {
  "kingsleyh/elm-json-transform": "1.0.5 <= v < 2.0.0"
}

Then run elm-install

Example

See the tests for example usage

raymanoz/elm-json-transform