kind-of/index.js

var toString = Object.prototype.toString;

/**
 * Get the native `typeof` a value.
 *
 * @param  {*} `val`
 * @return {*} Native javascript type
 */

module.exports = function kindOf(val) {
  // primitivies
  if (typeof val === 'undefined') {
    return 'undefined';
  }
  if (val === null) {
    return 'null';
  }
  if (val === true || val === false || val instanceof Boolean) {
    return 'boolean';
  }
  if (typeof val === 'string' || val instanceof String) {
    return 'string'
  }
  if (typeof val === 'number' || val instanceof Number) {
    return 'number'
  }

  // functions
  if (typeof val === 'function' || val instanceof Function) {
    return 'function'
  }

  // array
  if (typeof Array.isArray !== 'undefined' && Array.isArray(val)) {
    return 'array';
  }

  // check for instances of RegExp and Date before calling `toString`
  if (val instanceof RegExp) {
    return 'regexp';
  }
  if (val instanceof Date) {
    return 'date';
  }

  // other objects
  var type = toString.call(val);

  if (type === '[object RegExp]') {
    return 'regexp';
  }
  if (type === '[object Date]') {
    return 'date';
  }
  if (type === '[object Arguments]') {
    return 'arguments';
  }

  // buffer
  if (typeof Buffer !== 'undefined' && Buffer.isBuffer(val)) {
    return 'buffer';
  }

  // es6: Map, WeakMap, Set, WeakSet
  if (type === '[object Set]') {
    return 'set';
  }
  if (type === '[object WeakSet]') {
    return 'weakset';
  }
  if (type === '[object Map]') {
    return 'map';
  }
  if (type === '[object WeakMap]') {
    return 'weakmap';
  }
  if (type === '[object Symbol]') {
    return 'symbol';
  }

  // must be a plain object
  return 'object';
};