Simple JSON Templater

Keeps, drops and replaces JSON value/key pairs in function of given variables.

Installation

npm install simple-json-templater

Templating Language Specifications

The template is a JSON object that can contains meta keys which are the following:

• $keepIf
• $dropIf
• $replaceByValue
• $replaceByVariable

The meta keys describe how to build the final JSON. All meta keys are removed from the final JSON.

If you want to use a key that start with a dollar you can escape it by adding another dollar. Example:

{
  "abc": 123,
  "$$xyz": 456
}

gives:

{
  "abc": 123,
  "$xyz": 456
}

$replaceByValue

Can't be used concurrently with $replaceByVariable or $map.

The parent object will be replaced by the value. This is helpful in combinaison with $keepIf and $dropIf.

Example:

{
  "abc": [
    {
      "$replaceByValue": 123
    }
  ]
}

gives:

{
  "abc": [
    123
  ]
}

$replaceByVariable

Can't be used concurrently with $replaceByValue or $map.

The parent object will be replaced by the variable.

Example with var1 = "xyz":

{
  "abc": {
    "$replaceByVariable": "var1"
  }
}

gives:

{
  "abc": "xyz"
}

$map

Can't be used concurrently with $replaceByValue or $replaceByVariable.

Describe a variable wich its value will be maped by the $case meta keys. If no $case match the value, the $default meta key is used.

Example with var1 = "def":

{
  "xyz": {
    "$map": "var1",
    "$case:abc": 123,
    "$case:def": 456,
    "$default": 789
  }
}

gives:

{
  "xyz": 456
}

Example with var1 = "ghi":

{
  "xyz": {
    "$map": "var1",
    "$case:abc": 123,
    "$case:def": 456,
    "$default": 789
  }
}

gives:

{
  "xyz": 789
}

Example with var1 = "ghi" again but there is no $default key:

{
  "xyz": {
    "$map": "var1",
    "$case:abc": 123,
    "$case:def": 456
  },
  "uvw": [
    {
      "$map": "var1",
      "$case:abc": 123,
      "$case:def": 456
    }
  ]
}

gives:

{
  "uvw": [ null ]
}

$keepIf

Can't be used concurrently with $dropIf.

The parent object will be kept if and only if the expression is true.

Example with var1 = "xyz":

{
  "abc": {
    "$keepIf": "var1 is xyz",
    "$replaceByValue": 123
  },
  "def": {
    "$keepIf": "var1 isn't xyz",
    "$replaceByValue": 456
  }
}

gives:

{
  "abc": 123
}

$dropIf

Can't be used concurrently with $keepIf.

The parent object will be removed if and only if the expression is true.

Example with var1 = "xyz":

{
  "abc": {
    "$dropIf": "var1 is xyz",
    "$replaceByValue": 123
  },
  "def": {
    "$dropIf": "var1 isn't xyz",
    "$replaceByValue": 456
  }
}

gives:

{
  "def": 456
}

expression

An expression is a string that can have the following shape:

• <variable> is <value>
• <variable> isn't <value>

Variable and value can't have space.

Implementation

Import the parse function:

// like this
const { parse } = require('simple-json-templater');

// or like this
import { parse } from 'simple-json-templater';

Then use it:

/*

parse(
  template: { [key: string]: any },
  variables?: { [key: string]: string }
): any

*/

const result = parse({
  abc: {
    $replaceByVariable: 'var1'
  },
  xyz: [
    {
      $keepIf: 'var2 is keepFirst',
      $replaceByValue: 'first'
    },
    {
      $dropIf: 'var2 is keepFirst',
      $replaceByValue: 'second'
    }
  ]
}, {
  var1: '123',
  var2: 'keepSecond'
});

console.log(result);

/*

{
  abc: '123',
  xyz: [
    'second'
  ]
}

*/

Misc

contact: [email protected]
licence: GPL-3.0-or-later