Core TypeScript String (@luolapeikko/core-ts-string)

String type guards, assertions, and predicates for TypeScript applications.

Features

• Type guards for string validation
• Assertion functions that throw TypeError
• Predicate functions for functional programming
• Support for empty strings, case validation, and prefix/suffix checking

Installation

npm install @luolapeikko/core-ts-string

Full documentation

See https://luolapeikko.github.io/core-ts/ for detailed API documentation and usage examples for each package.

Usage

import {
  StringCore,
  StringAssert,
  StringPredicate,
} from "@luolapeikko/core-ts-string";

// Type guards
const value: unknown = "hello world";

if (StringCore.is(value)) {
  console.log(value.toUpperCase()); // value is typed as string
}

const emptyValue: unknown = "";
if (StringCore.isEmpty(emptyValue)) {
  console.log("Empty string"); // value is typed as EmptyString (or '')
}

// Predicates for filtering
const files = ["readme.md", "package.json", "src/index.ts"];
const markdownFiles = files.filter(StringPredicate.endsWith(".md")); // ['readme.md']

// Assertions
function processString(input: unknown) {
  StringAssert.assert(input); // First assert it's a string
  StringAssert.assertNotEmpty(input); // Then assert it's not empty
  return input.trim(); // input is now typed as non-empty string
}

// Example usage
const testInput = "test string";
const result = processString(testInput);
console.log("Processed string:", result);