Skip to content

Docs Tour Playground Errors Blog Community ★ 2GitHub

Documentation

Introduction
Language Reference
Examples
Type System
JavaScript & TypeScript Interop
Tooling
CLI Reference
Editor Setup
Changelog
Roadmap
Specification
FAQ

Roadmap

v1.0 RC Status

Operations

Playground Worker Deploy
Maintenance & On-Call
VS Code Marketplace

Launch

Launch drafts

Language Tour

Language Tour
01 — Hello world
02 — Variables and types
03 — Functions
04 — Control flow
05 — Null safety
06 — Pattern matching
07 — Sum types
08 — Object types
09 — Generics
10 — Classes
11 — Modules
12 — Async and await
13 — JSX
14 — Calling JS from SJS
15 — dynamic and Schema
16 — Errors and Result
17 — Iterators and for...of
18 — Serverless handlers
19 — Tooling tour
20 — Migrating a TS file

Press

README
sjs-vs-typescript-one-pager

Migration Guide

Migration Guide
Syntax Rewrites
Idiom Changes
Library Ecosystem

API Reference

API Reference
std-async
std-collections
std-core
std-fs
std-json
std-math
std-path
std-process
std-schema
std-string
std-time

Why SuperJS

Why SuperJS

Compatibility

Compatibility Matrix

Benchmarks

Performance Benchmarks
LSP Memory Audit

Error Codes

Error Codes
SJS-E001 — Null or undefined assigned to non-nullable type
SJS-E002 — Type mismatch
SJS-E003 — Property access on possibly-null value
SJS-E004 — `any` is not a valid type in SJS
SJS-E005 — Intersection type `A & B` is not allowed
SJS-E006 — Mapped type is not allowed in SJS
SJS-E007 — Non-exhaustive match expression
SJS-E008 — Conditional type is not allowed in SJS
SJS-E009 — `infer` keyword is not allowed in SJS
SJS-E010 — TypeScript `enum` is not allowed in SJS
SJS-E011 — Non-null assertion `!` is not allowed
SJS-E012 — `namespace` is not allowed in SJS
SJS-E013 — `with` statement not allowed (SJS is always strict mode)
SJS-E014 — Private or protected member not accessible from this scope
SJS-E015 — Cannot narrow an access modifier on an overriding method or property
SJS-E016 — Cannot instantiate an abstract class directly with `new`
SJS-E017 — Circular import detected — module graph contains a cycle
SJS-E018 — Top-level `await` used outside an ES module context
SJS-E019 — Unknown JSX element type — identifier not in scope or not a valid component
SJS-E020 — Ambiguous variant constructor
SJS-L001 — Prefer `const` — `let` binding is never reassigned
SJS-L002 — Prefer `let` or `const` over `var`
SJS-L003 — Use `===` / `!==` — `==` / `!=` performs type coercion
SJS-L004 — Prefer `for…of` over `for…in` for array and iterable iteration
SJS-L005 — `debugger` statement found in committed code
SJS-L006 — `match` expression has no arms
SJS-L007 — Redundant match arm
SJS-L008 — Prefer an arrow function callback
SJS-L009 — Unused import
SJS-L010 — Import out of order
SJS-L011 — BiDi control character rejected
SJS-L012 — Unused top-level declaration
SJS-L013 — Explicit `dynamic` type annotation
SJS-L014 — Variable shadowing
SJS-L015 — Floating promise
SJS-L016 — Unhandled `Result`
SJS-L017 — Prefer `Result` over `throw`
SJS-L018 — Mixed spaces and tabs in indentation
SJS-P001 — Unexpected token
SJS-P002 — Unexpected end of file
SJS-P003 — Invalid syntax in type annotation
SJS-P004 — Invalid sum type declaration
SJS-P005 — Invalid match expression
SJS-P099 — Too many parse errors; recovery abandoned
SJS-W001 — Implicit `dynamic` — unannotated position in `--strict` mode
SJS-W002 — `dynamic` value assigned to a typed position without a narrowing check
SJS-W003 — Unreachable `match` arm — earlier arm already covers this variant
SJS-W004 — Reserved or future SJS keyword used as an identifier
SJS-W005 — Explicit `public` modifier is redundant — class members are public by default
SJS-W006 — Excess property on a fresh object literal assigned to a typed position
SJS-W007 — Missing `key` prop on JSX element in a list or iterator context
SJS-W008 — Implicit switch fallthrough between non-empty case clauses
SJS-W009 — Unreachable code following a terminator statement
SJS-W010 — `catch` binding not typed as `Error` or `unknown` — untyped catch may hide bugs
SJS-W012 — BiDi control character in source file

Language Spec

Language Specification

Standard Library

Standard Library

Beta Program

Beta Program
Dynamic Usage Survey (C5)
Bug Bash

Standard Library

Reference documentation for all SuperJS standard library modules.

Content coming in WS-A4c.

Edit this page on GitHub

Documentation

Documentation

Introduction
Language Reference
Examples
Type System
JavaScript & TypeScript Interop
Tooling
CLI Reference
Editor Setup
Changelog
Roadmap
Specification
FAQ

Roadmap

v1.0 RC Status

Operations

Playground Worker Deploy
Maintenance & On-Call
VS Code Marketplace

Launch

Launch drafts

Language Tour

Language Tour
01 — Hello world
02 — Variables and types
03 — Functions
04 — Control flow
05 — Null safety
06 — Pattern matching
07 — Sum types
08 — Object types
09 — Generics
10 — Classes
11 — Modules
12 — Async and await
13 — JSX
14 — Calling JS from SJS
15 — dynamic and Schema
16 — Errors and Result
17 — Iterators and for...of
18 — Serverless handlers
19 — Tooling tour
20 — Migrating a TS file

Press

README
sjs-vs-typescript-one-pager

Migration Guide

Migration Guide
Syntax Rewrites
Idiom Changes
Library Ecosystem

API Reference

API Reference
std-async
std-collections
std-core
std-fs
std-json
std-math
std-path
std-process
std-schema
std-string
std-time

Why SuperJS

Why SuperJS

Compatibility

Compatibility Matrix

Benchmarks

Performance Benchmarks
LSP Memory Audit

Error Codes

Error Codes
SJS-E001 — Null or undefined assigned to non-nullable type
SJS-E002 — Type mismatch
SJS-E003 — Property access on possibly-null value
SJS-E004 — `any` is not a valid type in SJS
SJS-E005 — Intersection type `A & B` is not allowed
SJS-E006 — Mapped type is not allowed in SJS
SJS-E007 — Non-exhaustive match expression
SJS-E008 — Conditional type is not allowed in SJS
SJS-E009 — `infer` keyword is not allowed in SJS
SJS-E010 — TypeScript `enum` is not allowed in SJS
SJS-E011 — Non-null assertion `!` is not allowed
SJS-E012 — `namespace` is not allowed in SJS
SJS-E013 — `with` statement not allowed (SJS is always strict mode)
SJS-E014 — Private or protected member not accessible from this scope
SJS-E015 — Cannot narrow an access modifier on an overriding method or property
SJS-E016 — Cannot instantiate an abstract class directly with `new`
SJS-E017 — Circular import detected — module graph contains a cycle
SJS-E018 — Top-level `await` used outside an ES module context
SJS-E019 — Unknown JSX element type — identifier not in scope or not a valid component
SJS-E020 — Ambiguous variant constructor
SJS-L001 — Prefer `const` — `let` binding is never reassigned
SJS-L002 — Prefer `let` or `const` over `var`
SJS-L003 — Use `===` / `!==` — `==` / `!=` performs type coercion
SJS-L004 — Prefer `for…of` over `for…in` for array and iterable iteration
SJS-L005 — `debugger` statement found in committed code
SJS-L006 — `match` expression has no arms
SJS-L007 — Redundant match arm
SJS-L008 — Prefer an arrow function callback
SJS-L009 — Unused import
SJS-L010 — Import out of order
SJS-L011 — BiDi control character rejected
SJS-L012 — Unused top-level declaration
SJS-L013 — Explicit `dynamic` type annotation
SJS-L014 — Variable shadowing
SJS-L015 — Floating promise
SJS-L016 — Unhandled `Result`
SJS-L017 — Prefer `Result` over `throw`
SJS-L018 — Mixed spaces and tabs in indentation
SJS-P001 — Unexpected token
SJS-P002 — Unexpected end of file
SJS-P003 — Invalid syntax in type annotation
SJS-P004 — Invalid sum type declaration
SJS-P005 — Invalid match expression
SJS-P099 — Too many parse errors; recovery abandoned
SJS-W001 — Implicit `dynamic` — unannotated position in `--strict` mode
SJS-W002 — `dynamic` value assigned to a typed position without a narrowing check
SJS-W003 — Unreachable `match` arm — earlier arm already covers this variant
SJS-W004 — Reserved or future SJS keyword used as an identifier
SJS-W005 — Explicit `public` modifier is redundant — class members are public by default
SJS-W006 — Excess property on a fresh object literal assigned to a typed position
SJS-W007 — Missing `key` prop on JSX element in a list or iterator context
SJS-W008 — Implicit switch fallthrough between non-empty case clauses
SJS-W009 — Unreachable code following a terminator statement
SJS-W010 — `catch` binding not typed as `Error` or `unknown` — untyped catch may hide bugs
SJS-W012 — BiDi control character in source file

Language Spec

Language Specification

Standard Library

Standard Library

Beta Program

Beta Program
Dynamic Usage Survey (C5)
Bug Bash