🚀 Introducing sd-is v1.0.6: A Tiny JavaScript Utility for Type Checking, Smart Validation & Schemas

🔍 What is sd-is?

sd-is is a zero-dependency, blazing-fast JavaScript utility library for:

• ✅ Clean runtime type checks
• 🧠 Smart validation with auto-fix suggestions
• 📋 Schema definition + enforcement
• 🔒 Emoji-enhanced developer-friendly errors

It’s like typeof, instanceof, and Array.isArray — but smarter and cleaner.

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✨ What's New in v2.0+

Feature	Description
✅ assertType()	Enforce expected type at runtime
📋 defineSchema()	Declaratively define reusable schemas
🧪 validateAgainst()	Validate data against your schema (enums, custom, nested)
🧠 smartCheck	Check + explain + suggest fixes in human-readable format
➕ Bonus Checks	New utils: isDate, isPromise, isSymbol, isRegExp, listFunctions

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📦 Installation

npm install sd-is

Supports CommonJS, ESM, and is fully tree-shakable.

✅ Type Checking Basics

import {
  isString,
  isNumber,
  isBoolean,
  isUndefined,
  isNotUndefined,
  isEmptyObject,
  isEmptyArray,
  isPlainObject
} from 'sd-is';

console.log(isString('hello'));          // true
console.log(isNumber(123));              // true
console.log(isBoolean(false));           // true
console.log(isEmptyArray([]));           // true
console.log(isPlainObject({ a: 1 }));    // true
console.log(isUndefined(undefined));     // true
console.log(isNotUndefined(42));         // true

🧠 smartCheck: Check + Explain + Fix

import { smartCheck } from 'sd-is';

const result = smartCheck.isEmptyObject({ x: 1 });

console.log(result.ok);        // false
console.log(result.verdict);   // ❌ Not empty or not a valid object
console.log(result.reason);    // Found 1 key(s): x
console.log(result.fix());     // {}

🔒 assertType: Catch Mistakes Early

import assertType from 'sd-is/utils/assertType.js';

assertType('hello', 'string');       // ✅
assertType(42, 'string');            // ❌ Throws: expected 'string', got 'number'

📋 defineSchema + validateAgainst

import defineSchema from 'sd-is/utils/defineSchema.js';
import validateAgainst from 'sd-is/utils/validateAgainst.js';

const productSchema = defineSchema({
  id: { type: 'string' },
  price: { type: 'number', default: 0 },
  category: { type: ['string', 'undefined'], optional: true },
  tags: { type: 'array', default: [] },
  status: { enum: ['active', 'inactive'] },
  createdAt: {
    type: 'string',
    custom: (val) =>
      /\d{4}-\d{2}-\d{2}/.test(val) || 'Must be in YYYY-MM-DD format'
  }
});

const product = {
  id: 'p-001',
  price: 89,
  tags: ['electronics', 'sale'],
  status: 'active',
  createdAt: '2025-07-14'
};

const result = validateAgainst(productSchema, product);

console.log(result.ok);      // true
console.log(result.errors);  // []

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📚 All Available Utilities

Function	Description
isBoolean	Check for true/false
isNumber	Check if value is number
isString	Check if value is string
isUndefined	Check if value is undefined
isNotUndefined	Opposite of isUndefined
isNull	Check if value is null
isFunction	Check if value is function
isPlainObject	Check if object is a plain {}
isEmptyObject	Check if object has no keys
isEmptyArray	Check if array is empty
isDate	Check if value is a valid Date
isSymbol	Check if value is a Symbol
isPromise	Check if value is a Promise
isRegExp	Check if value is a RegExp
listFunctions	List all available util functions

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🤔 Why Use sd-is?

• 🔍 No need to write typeof value === 'string' everywhere
• 🧠 Helpful validation, with built-in defaults and messages
• ⚡ Extremely fast and tiny (~2KB gzipped)
• ✅ Perfect for API layers, CLI tools, or raw object validation
• 📦 No dependencies, supports modern JS without bloat

🔗 Links

📦 NPM: sd-is
💻 GitHub: github.com/sandeepdara-sd/sd-is

🙌 Wrap Up

If you're tired of verbose type checks and want a tiny, reliable, and developer-friendly utility for validating JavaScript structures — sd-is is for you.

Let me know what you think or contribute on GitHub! ⭐