Selecting Columns / Projecting

To select/deselect fields, you can use one of three methods: select, deselect and project.

Any column in MongoDB accepts dot notation selection by default, so feel free to use it.

select method

Let's start with select method, this method is the most comprehensive and easiest one to use to select or unselect columns.

Method signature:

  /**
   * Select the given columns
   */
  public select(columns: string[] | Record<string, 0 | 1 | boolean>): Aggregate;

The method accepts one of two types:

• array: an array of strings, each string is a column name that you want to select.
• object: If you want more control to what to select and what not to select use the object instead, this object should have the column name as a key, and the value should be one of the following:
  • 0: to exclude the column from the result.
  • 1: to include the column in the result.
  • true: to include the column in the result.
  • false: to exclude the column from the result.

deselect method

Deselect method accepts an array of columns strings that you want to exclude from the result.

Method signature:

  /**
   * Deselect the given columns
   */
  public deselect(columns: string[]): Aggregate;

project method

This is the native MongoDB method, it accepts an object that has the column name as a key, and the value could be any acceptable value in MongoDB Project Stage.

Method signature:

  /**
   * Project the given columns
   */
  public project(columns: Record<string, any>): Aggregate;