meta-ts

A package containing facilities for metaprogramming in typescript

Installation

npm install @huy-dna/meta-ts

Usage

The main checker is the two (dummy) functions checkAll and check:

checkAll<[
    Predicate,
    Predicate,
    Predicate,
]>

and

check<Predicate>

We can think of check and checkAll as:

• Compile-time functions - do not cause runtime overhead
• Arguments can be passed using <>.

Predicates

A predicate is an assertion about types.

A predicate P is said to be "true" if and only if check<P> pass the Typescript typechecker.

Currently, these predicates are supported:

SameType<T, S>

This predicate is true if T and S are the same type.

Example:

check<SameType<number, number>> // passed!
check<SameType<number, string>> // failed!

DoesExtend<T, S>

This predicate is true if T extends S.

Example:

check<DoesExtend<number, string>> // failed!
check<DoesExtend<3, number>> // passed!

SameNumericalEnum<T, S>

This predicate is true if enum T and enum S have the same keys with the same numerical value.

Example:

enum E1 {
    A,
    B,
    C
}

enum E2 {
    A = 0,
    B,
    C = 2,
}

check<SameNumericalEnum<E1, E2>> // passed!

Note that this only works with number-valued enums!

Pitfalls

• May not work correctly with any.

Contribution

This package is mainly built to tweak with the Typescript's typechecker.

Don't hesitate to challenge yourself and contribute some "predicate"s to this repo here: https://github.com/Huy-DNA/meta-ts.

Bug reports

Post an issues on the package's repo!