is.js

function is(type, object) {
  type = type[0].toUpperCase() + type.slice(1);
  var toString = Object.prototype.toString;
  return toString.call(object) === '[object ' + type + ']';
}
console.log(is('object', {})); // true
console.log(is('array', [])); // true
console.log(is('object', [])); // false
console.log(is('number', 2)); // true
console.log(is('number', '2')); // false