CtrlK
BlogDocsLog inGet started
Tessl Logo

tessl/npm-better-typescript-lib

An alternative TypeScript standard library with better type definitions

—

Pending

Quality

Pending

Does it follow best practices?

Impact

Pending

No eval scenarios have been run

SecuritybySnyk

Pending

The risk profile of this skill

Overview
Eval results
Files

Better TypeScript Lib

Better TypeScript Lib is an alternative TypeScript standard library that provides improved type definitions with better type safety. It replaces TypeScript's built-in any types with safer alternatives like JSONValue for JSON.parse() return values, and includes other improvements that became possible as TypeScript evolved.

Package Information

  • Package Name: better-typescript-lib
  • Package Type: npm
  • Language: TypeScript
  • Installation: npm install -D better-typescript-lib

Core Imports

For TypeScript 5.8+, add to your tsconfig.json:

{
  "compilerOptions": {
    "libReplacement": true
  }
}

For pnpm users, add to .npmrc:

public-hoist-pattern[]=@typescript/*

No explicit imports needed - the package automatically replaces TypeScript's built-in lib definitions through the @typescript/lib-* mapping mechanism.

Basic Usage

// JSON.parse now returns JSONValue instead of any
const data = JSON.parse('{"name": "Alice", "age": 30}');
// data is typed as JSONValue, not any

// eval returns unknown instead of any
const result = eval('2 + 2');
// result is typed as unknown, not any

// Better Object.hasOwnProperty type narrowing
const obj: unknown = { name: 'Bob' };
if (obj && typeof obj === 'object' && 'name' in obj) {
  // obj.name is now properly typed
}

Architecture

Better TypeScript Lib is built around several key components:

  • Lib Replacement System: Uses TypeScript 4.5+ compiler feature to detect and replace @typescript/lib-* packages
  • Type Safety Improvements: Replaces any with safer alternatives throughout the standard library
  • Build System: Generates individual npm packages from improved TypeScript lib definitions
  • Version Alignment: Tracks TypeScript releases while providing more frequent type definition improvements

The system works by mapping standard TypeScript lib imports to improved alternatives:

  • @typescript/lib-es5 → @better-typescript-lib/es5
  • @typescript/lib-dom → @better-typescript-lib/dom
  • etc.

Capabilities

Enhanced ES5 Core Library

Core JavaScript functionality with improved type safety, focusing on eval(), JSON interface, and Object methods with better type narrowing.

// JSON with safer types
interface JSON {
  parse(text: string): JSONValue;
  parse<T>(
    text: string,
    reviver: (this: any, key: string, value: JSONValueF<T>) => JSONValueF<T>
  ): JSONValueF<T>;
}

// Global functions with safer return types
declare function eval(x: string): unknown;

// Enhanced Object methods
interface Object {
  hasOwnProperty<Obj, Key extends PropertyKey>(
    this: Obj,
    v: Key
  ): this is Obj & (Key extends PropertyKey ? { [key in Key]: unknown } : {});
}

ES5 Core Library

JSON Type System

Comprehensive type definitions for JSON data structures, providing type-safe alternatives to any for JSON operations.

type JSONPrimitive = string | number | boolean | null;
type JSONValue = JSONPrimitive | JSONObject | JSONValue[];
type JSONObject = { [key: string]: JSONValue };
type JSONValueF<A> = JSONPrimitive | JSONComposite<A>;
type JSONHolder<K extends string, A> = Record<K, JSONValueF<A>>;

JSON Types

DOM and Web API Enhancements

Enhanced Body interface with safer JSON handling that returns JSONValue instead of any.

interface Body {
  json(): Promise<JSONValue>;
}

DOM Enhancements

ES2015+ Feature Improvements

Enhanced type definitions for modern JavaScript features including Promises, Collections, Iterables, and Symbols.

// Promise improvements
interface Promise<T> {
  then<TResult1 = T, TResult2 = never>(
    onfulfilled?: ((value: T) => TResult1 | PromiseLike<TResult1>) | null | undefined,
    onrejected?: ((reason: any) => TResult2 | PromiseLike<TResult2>) | null | undefined
  ): Promise<TResult1 | TResult2>;
}

ES2015+ Features

Typed Array Enhancements

Improved method signatures for typed arrays with better this typing and type safety.

interface TypedNumberArray<TArrayBuffer extends ArrayBufferLike = ArrayBufferLike> {
  every<This = undefined>(
    predicate: (this: This, value: number, index: number, array: this) => boolean,
    thisArg?: This
  ): boolean;
  
  filter<This = undefined>(
    predicate: (this: This, value: number, index: number, array: this) => boolean,
    thisArg?: This
  ): TypedNumberArray;
}

Typed Arrays

Types

Core Utility Types

/**
 * Type casting utility
 */
type Cast<T, U> = T extends U ? T : U;

/**
 * Make all properties in T writable
 */
type Writable<T> = {
  -readonly [P in keyof T]: T[P];
};

/**
 * Intersection of array types
 */
type Intersect<T extends readonly any[]> = ((
  ...args: { [K in keyof T]: Cast<Writable<T[K]>, {}> }
) => void) extends (...args: { [K in keyof T]: infer S }) => void
  ? S
  : never;

JSON Type Definitions

type JSONPrimitive = string | number | boolean | null;
type JSONComposite<A> = { [key: string]: JSONValueF<A> } | JSONValueF<A>[];
type JSONValueF<A> = JSONPrimitive | JSONComposite<A>;
type JSONValue = JSONPrimitive | JSONObject | JSONValue[];
type JSONObject = { [key: string]: JSONValue };
type JSONHolder<K extends string, A> = Record<K, JSONValueF<A>>;
Workspace
tessl
Visibility
Public
Created
Last updated
Describes
npmpkg:npm/better-typescript-lib@2.11.x
Publish Source
CLI
Badge
tessl/npm-better-typescript-lib badge