CoffeeScript To TypeScript Features

This is a running list of supported and not-yet-supported features on my typescript branch. See this wiki page for another list of TypeScript features.

Types

• Primitive types given by any identifier: any, unknown, object, void, never, number, string, boolean, bigint, symbol, Function
• Literal types: numbers, strings, booleans, and within typeof, Infinity, NaN
• null, undefined, and void types
• Function types: (arg1 ~ ArgType, arg2 ~ ArgType) -> returnType (or ditto with =>)
  • Optional parameters: (arg? ~ ArgType) ~ ReturnType -> ...
• Constructor type: new ...
• Array types: baseType[]
• Tuple types: [name ~ string, age ~ number]
• Object types, including optional properties: {key: string, value?: number} or omitting braces as usual in CoffeeScript:

  key: string
  value?: number

  • [keyExpr]: value
• Union types: type1 | type2
• Intersection types: type1 & type2
• keyof, unique, readonly operators
• Type indexing: T["key"]
• Namespace dereferencing: space.T
• Mapped types: {[Key in keyof Type]: ...}
• typeof operator
• Template types, e.g. ReturnType<T>, Partial<T>, Required<T>, Readonly<T>, Record<K,T>, Pick<T,K>, Omit<T,K>, Iterable<T>, ...
• Conditional types: if { legs: 4 } then Animal else never
• Template string types: "index.#{"en" | "fr"}.html"
• extends assertion: T extends S
• TypeScript passthrough: `passthrough code`

Type Annotation

• ~ or := assigning type to a variable: variable ~ Type
• Assigning to variable as it's typed: variable ~ Type = value
  • After-indented-type next-line assignment:

    variable ~
      key: string
      value?: number
    =
      key: 'hello'
      value: 7

• Function typing (arg1 ~ ArgType, arg2 ~ ArgType) ~ ReturnType -> ...
  • Optional parameters: (arg? ~ ArgType) ~ ReturnType -> ...
• Generic functions: f = <T>(a ~ T[]) ~ T -> a[0]
• Function overloads?
• Class attributes via x ~ T
• Generic classes: class Box<T>
• class ... implements ...
• Type guards: (obj) ~ obj is Response -> (conflict with CoffeeScript is?)
• Type assertions: (obj) ~ asserts obj is Response

Type Definitions

• type
  • Leading | in multiline unions
  • Template types: type Foo<T>
  • extends
• interface
  • Template interfaces: interface Foo<T>
  • extends
• import type
• declare
• module
• namespace

Type Casting

• Nonnull assertion: !
• as
• as const

Nontype features

• private, protected, public, readonly variable modifiers
• enum
• #@tsc-ignore
• #/ <directive />