ECMA Alignment

How Tish maps to ECMA-262 and test262.

This page summarizes Tish behavior relative to ECMA-262. Each concept has a decision: Follow, Omit, or Simplify.

Types

Undefined → Null (Tish uses null only; typeof null returns "null", not "object")
Boolean, Number, String, Object — Follow
No Symbol, BigInt in MVP

Equality and coercion

Strict equality only (===, !==)
No loose equality (==)
No implicit coercion

Expressions and statements

Category	Decision
block, break, continue, for, if, return, while	Follow
switch, do-while	Follow
throw, try/catch	Follow
addition, array, assignment, call	Follow
coalesce (`??`), conditional (`? :`)	Follow
member, optional-chaining (`?.`)	Follow
class, new, super, this	Omit
async, await	Follow (simplify)
generators	Omit
for-in	Omit; for-of follows (arrays and strings)

Builtins

Builtin	Decision
Array, Math, String, Object	Follow (simplify)
JSON (parse, stringify)	Follow
console	Follow (with TISH_LOG_LEVEL)
parseInt, parseFloat, isFinite, isNaN	Follow
encodeURI, decodeURI	Follow
Promise	Follow (§27.2): constructor, .then, .catch, .finally, resolve, reject, all, race. Host: setTimeout, setInterval, clearTimeout, clearInterval (non-blocking; callbacks run after delay)
Proxy, Reflect, Symbol	Omit
RegExp	Optional (regex feature)

Tish-specific

fn / function — both supported
Optional braces (indentation)
Tab/space normalized
No this, with, eval
No var — let/const only

For the full alignment document, see the tish/docs/ecma-alignment.md in the tish repo.