transform.js

Transform

transform operates on arrays of objects and lets you

• cherry pick (nested) keys that your objects should include
• define functions that transform values of a given key, and possibly alters the key as well.
• map a value to a new key
• omit keys from the objects.

Transform will hopefully in the future also be able to:

• omit nested keys from the objects.

Usage

To install run npm install transform.js,

and to use transform do

var transform = require('transform.js');

Roughly speaking transform is a function that accepts three parameters

1. the data array
2. the fields that should be included, and/or mapped
3. the fields that should be ommited.

I think of it as

transform(data, include, exclude)

Behaviour

If the last two parameters are ommited transform will return a clone of the data object.

var cloned = transform(data);

If the the second parameter is a string or a list of keys, the given keys will be cherry picked from each object in the data array, and the third parameter will be ignored:

transform(data, ['x', 'y'])  // only keep fields 'x' and 'y'
transform(data, 'x') // only keep field 'x'
transform(data, 'x.x') // only keep 'x.x'

If the second parameter is falsy, and the third parameter is a string or list of keys, the given keys will be ommitted from each object in the data array. (Note: does not accept nested keys as of now)

transform(data, null, ['x']]);

Now the interesting part begins. If the second parameter is an object, the behaviour changes a bit.

To transform the values of keys 'x' and 'y', but leave out all other fields do

transform(data, {
  x: (val) => val + 1, 
  y: (val) => val + 1
}, true);

To transform the values of keys 'x' and 'y', but include all other fields do

transform(data, {
  x: (val) => val + 1, 
  y: (val) => val + 1
});

To map a value to a new key (and include all other field) do

transform(data, {
  x: 'y',
  y: 'x'
});

Or, if you need to both transform and map to a new key do

transform(data, {
  x: (val) => ({key: 'y', value: val + 1}),
  y: (val) => ({key: 'x', value: val + 1})
});