Getting Started

The class-transformer package is a zero-dependency utility library helping you to quickly transform class instances to plain objects and vice-versa. It works well with the class-validator library. The main features include:

• conditionally transforming object properties

• excluding specific properties from the transformed object

• exposing properties under a different name on the transformed object

• supports both NodeJS and browsers

• fully three-shakable

• zero external dependencies

Installation

To start using class-transformer install the required packages via NPM:

npm install class-transformer reflect-metadata

Import the reflect-metadata package at the first line of your application:

import 'reflect-metadata';

// Your other imports and initialization code
// comes here after you imported the reflect-metadata package!

As the last step, you need to enable emitting decorator metadata in your Typescript config. Add these two lines to your tsconfig.json file under the compilerOptions key:

"emitDecoratorMetadata": true,
"experimentalDecorators": true,

Now you are ready to use class-transformer with Typescript!

Basic Usage

The most basic usage is to transform a class to a plain object:

import { Expose, Exclude, classToInstance } from 'class-transformer';

class User {
  /**
   * When transformed to plain the `_id` property will be remapped to `id`
   * in the plain object.
   */
  @Expose({ name: 'id' })
  private _id: string;

  /**
   * Expose the `name` property as it is in the plain object.
   */
  @Expose()
  public name: string;

  /**
   * Exclude the `passwordHash` so it won't be included in the plain object.
   */
  @Exclude()
  public passwordHash: string;
}

const user = getUserMagically();
// contains: User { _id: '42', name: 'John Snow', passwordHash: '2f55ce082...' }

const plain = classToInstance(user);
// contains { id: '42', name: 'John Snow' }