Syntax Overview

FScript uses a small, expression-oriented syntax with arrows, immutable bindings, records, arrays, pattern matching, and explicit imports.

A compact tour

import Array from 'std:array'
import Logger from 'std:logger'

type User = {
  id: String,
  name: String,
  active: Boolean,
}

formatNames = (users: User[]): String[] => users
  |> Array.filter((user) => user.active)
  |> Array.map((user) => user.name)

main = (): Undefined => {
  names = formatNames([
    { id: '1', name: 'Ada', active: true },
    { id: '2', name: 'Grace', active: false },
  ])

  Logger.info(names)
}

main()

Forms you will use most

import and export for modules
name = expression for immutable bindings
type Name = ... for type aliases
(args): Return => expr for functions
{ ... } for records and block expressions
[ ... ] for arrays
if (...) { ... } else { ... } for conditional expressions
match (value) { ... } for pattern-based branching
|> for pipe-based composition

Major differences from JavaScript or TypeScript

no function keyword
no return
no let, const, or var
no class syntax
no array or object prototype methods
no async / await

Reading the rest of the guide

If you are new to FScript, a useful order is: