what is the best way to check variable type in javascript

Answer 1

ES-Next version with support BigInt & Symbol

"use strict";

/**
 *
 * @author xgqfrms
 * @license MIT
 * @copyright xgqfrms
 * @created 2020-06-09
 * @modified
 *
 * @description js data type checker
 * @augments
 * @example
 * @link
 *
 */


const dataTypeChecker = (data, debug = false) => {
  const log = console.log;
  let result = ``;
  const typeString = Object.prototype.toString.call(data);
  result = typeString.replace(/\[object /gi, ``).replace(/\]/gi, ``);
  if(debug) {
    log(`true type`, result)
  }
  return result;
};



export default dataTypeChecker;

export {
  dataTypeChecker,
};

test

const dataTypeChecker = (data, debug = false) => {
  const log = console.log;
  let result = ``;
  const typeString = Object.prototype.toString.call(data);
  // const typeString = Object.prototype.toString.apply(data);
  result = typeString.replace(/\[object /gi, ``).replace(/\]/gi, ``);
  if(!debug) {
    log(`true type`, result)
  }
  return result;
};



const obj = {};
const func = () => {};


dataTypeChecker(NaN)
//"[object Number]"
dataTypeChecker(undefined)
//"[object Undefined]"
dataTypeChecker(true)
//"[object Boolean]"
dataTypeChecker({})
//"[object Object]"
dataTypeChecker(func)
//"[object Function]"
dataTypeChecker(obj)
//"[object Object]"
dataTypeChecker(Symbol())
//"[object Symbol]"
dataTypeChecker(null)
//"[object Null]"
dataTypeChecker(123)
//"[object Number]"
dataTypeChecker(BigInt(1n))
//"[object BigInt]"


// true type Number
// true type Undefined
// true type Boolean
// true type Object
// true type Function
// true type Object
// true type Symbol
// true type Null
// true type Number
// true type BigInt