object-unpacker

TypeScript Object Unpacker

This program takes a JSON object and convertes it to a new JSON object using a mapping specification, also written as JSON.

There are some examples of how to use the mapper in the test directory, and a simple TypeScript example follows:

// Import the Schema Mapper type
import { createObjectUnpacker } from '../src/ObjectUnpacker';
import { ProcedureInstruction } from '../src/instructions';

// Create the schema mapper
const mapper = createObjectUnpacker();

// This is the data to be transformed
const data = {
  "x": [
    {
      "a": [
        "testa",
        "testb"
      ],
      "au": "%system.metadata.author"
    }
  ]
};

// This is the transformation specification
const mapperData: ProcedureInstruction = [
  {
    comment: 'Create the top level result object',
    action: 'toObject',
    source: '/compact',
    target: '/expanded',
    keys: ['x'],
    values: {
      formatted: '%x'
    }
  },
  {
    comment: 'process the `formatted` array',
    action: 'foreach',
    source: '/expanded.formatted',
    target: '/expanded.formatted',
    loopVar: 'i',
    instruction: [
      {
        comment: 'process the array entry',
        action: 'toObject',
        source: 'i',
        target: 'tmp',
        keys: ['a', 'au'],
        values: {
          another:{
            first:'%a.0',
            second:'%a.1',
            fourth:'%/subs.system.metadata.name'
          },
          author:'%au'
        }
      }
    ]
  }
];

// Entries in this object can be referenced by the `data` or the `mapperData`.
// E.g. `%system.metadata.name` and '%system.metadata.author'
const refs = {
  system: {
    metadata: {
      name: 'The System Name',
      author: 'A. Programmer',
    },
  },
};

// Apply the mapping to the data to get an `expanded` object
const expanded: object = mapper.convert(refs, data, mapperData);

// Pretty-print the resulting JSON.
console.log(JSON.stringify(expanded, null, 2));

The same example in JavaScript

const unpacker = require("object-unpacker")

// This is the data to be transformed
const data = {
  "x": [
    {
      "a": [
        "testa",
        "testb"
      ],
      "au": "%system.metadata.author"
    }
  ]
};

// This is the transformation specification
ProcedureInstruction = [
  {
    comment: 'Create the top level result object',
    action: 'toObject',
    source: '/compact',
    target: '/expanded',
    keys: ['x'],
    values: {
      formatted: '%x'
    }
  },
  {
    comment: 'process the `formatted` array',
    action: 'foreach',
    source: '/expanded.formatted',
    target: '/expanded.formatted',
    loopVar: 'i',
    instruction: [
      {
        comment: 'process the array entry',
        action: 'toObject',
        source: 'i',
        target: 'tmp',
        keys: ['a', 'au'],
        values: {
          another:{
            first:'%a.0',
            second:'%a.1',
            fourth:'%/subs.system.metadata.name'
          },
          author:'%au'
        }
      }
    ]
  }
];
// Entries in this object can be referenced by the `data` or the `mapperData`.
// E.g. `%system.metadata.name` and '%system.metadata.author'
const refs = {
  system: {
    metadata: {
      name: 'The System Name',
      author: 'A. Programmer',
    },
  },
};

// Apply the mapping to the data to get an `expanded` object
const expanded = unpacker.mapper.convert(refs, data, mapperData);

// Pretty-print the resulting JSON.
console.log(JSON.stringify(expanded, null, 2));

Running the example code

1. Run npm install
2. Create scratch.ts in the src directory.
3. Compile it using the tsc command
4. Run it using node dist/scratch.js
5. Or combine the previous two steps as tsc && node dist/scratch.js

The output should look like this:

{{
  "formatted": [
    {
      "another": {
        "first": "testa",
        "second": "testb",
        "fourth": "The System Name"
      },
      "author": "A. Programmer"
    }
  ]
}

Running the example code in a web browser

1. Run npm install
2. Run npm install -g webpack
3. Run npm install -g webpack-cli
4. Run the webpack command in the project root directory.
5. Open the test/index.html file using a web browser (Only tested using Brave browser)
6. Paste your JSON into the first two text areas and click Execute