JS Model Mapper

A simple data mapper for javascript. You can use to format a data to your API or format the response from your API too.

Installation

npm install js-model-mapper or yarn js-model-mapper

Usage

You can use JS Model Mapper for many cases in your application. Bellow we have some examples:

Simple mapper

If you want to ignore some fields of your object, you can use a mapper to just collect the relevant fields for you.

const parse = mapper([
  'name', 
  'surname'
]);
const output = parse({ 
  name: 'John', 
  surname: 'Snow', 
  nonRelevantItem: 'No ones care'
});
 
/*
  output will be: { 
    name: 'John', 
    surname: 'Snow',
  }
*/;

If you have an optional field in your object and just need to send if this field exists, you can specify in your mapper this property and this behavior will occurs.

const parse = mapper([
  'name', 
  'surname', 
  'createdAt'
]);
 
let output = parse({ 
  name: 'John', 
  surname: 'Snow', 
});
 
/* 
  output will be: { 
    name: 'John', 
    surname: 'Snow',
  };
*/
 
output = parse({ 
  name: 'John', 
  surname: 'Snow', 
  createdAt: '1979-01-01T00:00:00.000Z'
});
 
/* 
  output will be: { 
    name: 'John', 
    surname: 'Snow', 
    createdAt: '1979-01-01T00:00:00.000',
  };
*/

If your property is a nested property, you can pass the property path:

const parse = mapper(['author.name']);
const output = parse({ 
  author: { 
    name: 'Martin Fowler',
    age: 20,
  },
});
 
/* 
  output will be: { 
    author: { 
      name: 'Martin Fowler'
    } 
  }
*/

Mapper with rename

Sometimes, you need to rename a property from an object to another name in output object. If you need this, you can provide a object in mapper options. If you send a property from with original field name and a property name with target property name, the mapper will rename this field.

const parse = mapper([{
  name: 'title',
  from: 'bookName',
}]);
 
const output = parse({ 
  bookName: 'Fahrenheit 451',
});
 
/*
  output will be: {
    title: 'Fahrenheit 451',
  };
*/

In some cases, maybe you need to rename from a nested property to a non nested property in your final object.

const parse = mapper([{
  name: 'publisher',
  from: 'publisher.name',
}]);
 
const output = parse({ 
  publisher: {
    name: 'Ballantine Books',
  },
});
 
/*
  output will be: {
    publisher: 'Ballantine Books',
  };
*/

If you need to get a non nested property and map to a nested property, this will works too:

const parse = mapper([{
  name: 'publisher.name',
  from: 'publisherName',
}]);
 
const output = parse({ 
  publisherName: 'Ballantine Books',
});
 
/*
  output will be: {
    publisher: {
      name: 'Ballantine Books',
    },
  };
*/

Mapper with transformation

In some cases, you can need to transform your mapped field. An example is a scenario when you need to convert the date to an ISO-8601 format.

const parse = mapper([{
  name: 'createdAt',
  transform: fieldValue => fieldValue.toISOString();
}]);
 
const output = parse({ 
  createdAt: new Date(),
});
 
/*
  output will be: {
    createdAt: (new Date()).toISOString(),
  };
*/

** Note: When you don't send from property, the value of from will be the value of name property.

If for some reason, you need to have access of full object to transform your data, you can access as a second args in transform function.

const parse = mapper([{
  name: 'fullName',
  from: 'name',
  transform: (fieldValue, obj) => `${fieldValue} ${obj.surname}`,
}]);
 
const output = parse({ 
  name: 'John',
  surname: 'Snow',
});
 
/*
  output will be: {
    fullName: 'John Snow',
  };
*/

Mapper when applicable

In some scenarios, you can need to conditionate the field before apply. If you have, for example, a message available to some countries, you need to compare a country field before apply the property in a final object.

const worldCupChampions = [
  'Uruguay', 
  'Italy', 
  'Germany', 
  'Brazil', 
  'England', 
  'Argentina', 
  'France', 
  'Spain',
];
 
const parse = mapper([{
  name: 'message',
  shouldApply: {
    field: 'country',
    condition: fieldValue => worldCupChampionsArray.includes(fieldValue)
  },
}]);
 
const output = parse({ 
  country: 'Brazil',
  message: 'You have won a Football World Cup!'
});
 
/*
  output will be: {
    message: 'You have won a Football World Cup!',
  };
*/

**Note: If you need to transform this field, the transformation will be applied only if condition is satisfied.

Contributing

If you want to contribute to js-model-mapper, check the file CONTRIBUTE.md to learn how to contribute.