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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;