var color = "red";
var color2 = {};
color instanceof String // will return true
color2 instanceof Object // will return true


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function Phone(serial, price, color){
  this.serial = serial;
  this.price = price;
  this.color = color;
}

let phone1 = new Phone('abc1', 200, 'red');
let phone2 = new Phone('abc2', 400, 'green');

//instanceof 
console.log(phone1 instanceof Phone) // true

//constructor
console.log(phone1.constructor === Phone) //true