Shapeshifter.js

A mini Typescript/Javascript library that helps you transform objects faster & easier.

Table of Contents

• Installation
• Usage
• Transformation schema
  • Just copy an attribute
  • Rename an attribute
  • Use a mapping function
  • Full definition
• Advanced settings
  • Nested transformation
  • Virtual attributes

Installation

Using npm

npm install @necrobits/shapeshifter

or using yarn

yarn add @necrobits/shapeshifter

Usage

// Create a shapeshifter using a schema
const shapeshifter = Shapeshifter.create(schema);
// Transform the data
const newData = shapeshifter.transform(data);

Transformation schema

schema is an object that describes the transformation. There are different ways to define it. Usually, the keys in the schema are the attribute names in the object. There is an exception for virtual attributes, we will come back to that later on. Now let's learn some simple syntax first.

Just copy an attribute

Just use true to tell the Shapeshifter to copy the attribute.

{
   my_attribute : true
}

Rename an attribute

Simply write the new name as value

{
    my_attribute: "my_new_attribute"
}

Use a mapping function

Yes, you can also use a function to map the value

{
    my_attribute: (value) => `This is a new ${value}`
}

Sometimes, you want to construct the value based on other fields. That's the time to utilize the 2. argument in the mapping function. This example transforms the first name field into full name.

{
    first_name: (first_name, obj) => `${first_name} ${obj.last_name}`
}

Full definition

The 3 variants above is a shorthand version for convenience and compactness. You can define the transformation using the full version like this:

{
    my_attribute: {
        to: "my_new_attribute",
        mapping: (value) => `This is a new ${value}`
    }
}

Advanced settings

Nested transformation

You can define a nested transformation rule using the magic key __nested__.

• If parents is only a object, the Shapeshifter will transform it as usual.
• If parents is an array of multiple parent objects, the Shapeshifter will automatically apply a map function on the array to transform every element in the array.

{
    first_name: true,
    last_name: true,
    parents: {
        __nested__: true,
        first_name: true,
        last_name: true
    }
}

Virtual attributes

It's kinda irrational to transform first_name into full_name in the above example.
What if you want to keep first_name, last_name but also want to create a new field called full_name? That's where virtual attributes come into play. With virtual attributes you can define new attributes. Because those attributes are not created based on any old attributes, so we call them "virtual".

In order to define virtual attributes, you need to use the following format __virtual<name>__. For example:

{
    first_name: true,
    last_name: true,
    __virtual_fullname__: {
        to: "full_name",
        mapping: (_, obj) => `${obj.first_name} ${obj.last_name}`
    },
    __virtual_fullname2__: {
        to: "full_name_uppercase",
        mapping: (_, obj) => `${obj.first_name} ${obj.last_name}`.toUpperCase()
    }
}

License

MIT