utils.md

Utils

This package contains some common utility functions that can be used by both users and implementors of the Facade.

• convertPropertyFilter
• createCursorFromEntity
• createCursorsFromEntities
• createGetEntitiesResult
• createPaginationFilter

convertPropertyFilter

Converts the filter value for a certain property name. For example, if you have a date property on your entity called createdAt storing the date at which an entity was created, then if you filter the property using a string (usually via js-entity-repos/express), you can use this util to ensure that the string is converted to a date before using the filter in the database. This is usually used by users of the js-entity-repos inside a constructFilter function in the factory config of concrete implementations of the Facade, the Knex implementation allows this configuration function amongst others.

import convertPropertyFilter from '@js-entity-repos/core/dist/utils/convertPropertyFilter';

convertPropertyFilter({
  converter: (value: any) => new Date(value),
  propertyName: 'createdAt',
  filter: { createdAt: '2018-01-01' },
});
// Returns the result of { createdAt: new Date('2018-01-01') }

createCursorFromEntity

Exactly what it says on the tin, this creates a cursor from an entity. A cursor is constructed by creating a filter that will filter out entities not expected in the next set of paginated results. This filter is then stringified to JSON and base 64 encoded. This function is usually used by the createCursorsFromEntities util. Check out the createCursorsFromEntities implementation for an example of its use.

createCursorsFromEntities

Creates a forwardCursor and a backwardCursor from an array of entities along with a sort and cursor. This function is usually used by the createGetEntitiesResult util. Check out the createGetEntitiesResult implementation for an example of its use.

createGetEntitiesResult

This function is usually used by concrete implementations of the Facade to construct the result for a request to get entities. Check out Knex's getEntities implementation for an example of its use.

createPaginationFilter

Takes a pagination option and a sort option) to produces a filter that can filter out entities not expected in the next set of paginated results. This function is usually used by concrete implementations of the Facade like Knex's getEntities implementation.

import createPaginationFilter from '@js-entity-repos/core/dist/utils/createPaginationFilter';
import { start } from '@js-entity-repos/core/dist/types/Cursor';
import { asc, desc } from '@js-entity-repos/core/dist/types/SortOrder';
import { backward, forward } from '@js-entity-repos/core/dist/types/PaginationDirection';

createPaginationFilter(
  { cursor: start, direction: forward, limit: 1 },
  { id: asc, numberProp: desc }
);
// Returns {}

createPaginationFilter(
  { cursor: forwardCursor, direction: forward, limit: 1 },
  { id: asc, numberProp: desc }
);
// Returns the result of { id: { $gt: lastEntity.id }, numberProp: { $lte: lastEntity.numberProp } }

createPaginationFilter(
  { cursor: backwardCursor, direction: backward, limit: 1 },
  { id: asc, numberProp: desc }
);
// Returns the result of { id: { $lt: firstEntity.id }, numberProp: { $gte: firstEntity.numberProp } }