Getting started in TypeScript

The quickest way to start experimenting with Bmg.js is to create a simple script and set up a relation.

Installation

npm install @enspirit/bmg-js

Basic Usage

my_bmg_script.ts

import { Bmg } from '@enspirit/bmg-js'

const suppliers = Bmg([
  { sid: "S1", name: "Smith", status: 20, city: "London" },
  { sid: "S2", name: "Jones", status: 10, city: "Paris"  },
  { sid: "S3", name: "Blake", status: 30, city: "Paris"  },
  { sid: "S4", name: "Clark", status: 20, city: "London" },
  { sid: "S5", name: "Adams", status: 30, city: "Athens" }
])

const byCity = suppliers
  .exclude({ status: 30 })
  .extend({ upname: (t) => t.name.toUpperCase() })
  .group(['sid', 'name', 'upname', 'status'], 'suppliers_in')

console.log(JSON.stringify(byCity.toArray(), null, 2))

This script will output:

[
  {
    "city": "London",
    "suppliers_in": [
      {
        "sid": "S1",
        "name": "Smith",
        "status": 20,
        "upname": "SMITH"
      },
      {
        "sid": "S4",
        "name": "Clark",
        "status": 20,
        "upname": "CLARK"
      }
    ]
  },
  {
    "city": "Paris",
    "suppliers_in": [
      {
        "sid": "S2",
        "name": "Jones",
        "status": 10,
        "upname": "JONES"
      }
    ]
  }
]

Here, we created a relation from an array of objects. The Bmg function wraps an array into a Relation that provides all relational operators.

TypeScript Support

Bmg.js provides full TypeScript support with generic types:

import { Bmg } from '@enspirit/bmg-js'

interface Supplier {
  sid: string
  name: string
  status: number
  city: string
}

const suppliers = Bmg<Supplier>([
  { sid: 'S1', name: 'Smith', status: 20, city: 'London' },
])

// Type-safe operations with autocomplete
const projected = suppliers.project(['sid', 'name'])
// Type: Relation<{ sid: string; name: string }>

const one = suppliers.restrict({ sid: 'S1' }).one()
// Type: Supplier

Standalone Operators

You can also use operators as standalone functions on plain arrays:

import { restrict, project } from '@enspirit/bmg-js'

const suppliers = [
  { sid: 'S1', name: 'Smith', city: 'London' },
  { sid: 'S2', name: 'Jones', city: 'Paris' },
]

const result = project(restrict(suppliers, { city: 'Paris' }), ['name'])
// => [{ name: 'Jones' }]