Javascript TypeCheck

typeCheck.js

module.exports = function typeCheck(...args) {
	args.map(({
		param,
		expected
	}) => {
		var type = Array.isArray(param) ? 'array' : typeof param;

		if (Array.isArray(expected)) {
			if (expected.indexOf(type) < 0) {
				throw new SyntaxError(`Expected ${expected.join( expected.length > 1 ? ' or ' : '')} saw ${type}`);
			}

			return;
		} else {
			if (expected !== type) {
				throw new SyntaxError(`Expected ${expected} saw ${type}`)
			}

			return;
		}
	})

	return;
}

typeCheck.ts

interface Argument {
	param: any,
	expected: String[] | String
}

export default function typeCheck(...args: Argument[]): void {
	args.map(({param, expected}) => {
		var type = Array.isArray(param) ? 'array' : typeof param;

		if ( Array.isArray(expected) ) {
			if ( expected.indexOf(type) < 0 ) {
				throw new SyntaxError(`Expected ${expected.join( expected.length > 1 ? ' or ' : '')} saw ${type}`);
			}

			return;
		} else {
			if ( expected !== type ) {
				throw new SyntaxError(`Expected ${expected} saw ${type}`)
			}

			return;
		}
	})

	return;
}

Usage.md

Usage

Use it like:

  import typeCheck from './typeCheck';

  /**
   * @name round
   * @description Write a function that round a number (`n`) to given decimal places.
   *
   * 
   * @example Usage:
   * round(Math.PI, 2) // => 3.14
   * 
   * 
   * @param {Number} n The number to be rounded
   * @param {Number} places Decimal places
   * 
   * @returns {Number} Rounded number
   */

  module.exports.round = function (n, places = 0) {
    typeCheck({
      param: n,
      expected: 'number'
    }, {
      param: places,
      expected: 'number'
    })

    places = Math.pow(10, places)

    return Math.floor(n * places) / places;
  }