ProjectionOperator type

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ProjectionOperator type

Represents a projection operator used in database queries or data transformations.

A projection operator is an object where keys are operator names starting with a dollar sign ($), and values can be: - DocumentPath: References to fields (e.g., '$_id', '$user.name') - Arrays: For operators like $concat that take multiple arguments - Nested operators: For composed operations - Primitive values: For literal values

Common operators include: - Type conversion: $toString, $toInt, $toBool - String operations: $concat, $substr, $toLower, $toUpper - Custom operators: $hexToBase64Url - Logical operators: $eq, $ne, $and, $or

Signature:

type ProjectionOperator = {
    [operator: `$${string}`]:
        | DocumentPath
        | ProjectionOperator
        | Array<DocumentPath | ProjectionOperator | string | number | boolean>
        | string
        | number
        | boolean;
};

References: DocumentPath, ProjectionOperator

Example

// Simple field reference
const simpleOp: ProjectionOperator = {
    $toString: '$_id'
};

// String concatenation
const concatOp: ProjectionOperator = {
    $concat: ['$firstName', ' ', '$lastName']
};

// Nested operators
const nestedOp: ProjectionOperator = {
    $concat: [{ $hexToBase64Url: '$_id' }, '_', '$members.id']
};