Map / Transform

Map values in a source object, optionally transform it using your own function, put it in a new object.

Installation

$ npm install maptrans

Usage

The first thing you do is to create a new MapTrans object with a "map". The map is an array of objects that describe how you want to transform the old object into a new one.

var maptrans = require('maptrans');
var map = maptrans([
  {
    source: '$.json.path.string',
    target: {
      op: 'add',
      path: '/foo'
    }
  },
  {
    source: '$.json.path.string',
    target: {
      op: 'add',
      path: '/bar'
    },
    transform: function (value, map, source) {
      return value.toUpperCase();
    }
  }
]);

var mapped = map.map(yousuperobject);
var another = map.map(anothersuperobject);

A short hand syntax for add operations can be used like this:

{
  source: '$.foo',
  target: '/foo'
}

API

The maptrans() function takes an array of mapping definitions. The mapping definitions must contain source and target. source is a JSON Path string. target is a JSON Patch object.

The value of source will be added to your target and is then applied to the result object.

Note that target can also be an array of patch objects if you need to do fancy stuff.

Transforms

A transform property may also be added to your mapping definition. The property must contain a function. An example transform function might look like this:

function (value, map, source, result) {
  return value.toUpperCase();
}

The this context for the transformation function is set to the mapping definition the function is attached to. It's arguments will be:

• The current value being mapped.
• The original map.
• The source, the entire object being mapped.
• The result object as it looks "so far".

License

MIT