weird output by instanceof in javascript

Question

when I am doing the following snippet

var name = new String("NewDelhi");
var count = new Number(10);
console.log(name instanceof String); //false
console.log(count instanceof Number); //true

when I am using name as variable it showing me false while giving it some other variable it showing true

var str = new String("NewDelhi");
var count = new Number(10);
console.log(str instanceof String); //true
console.log(count instanceof Number); //true

why is this happening.

Answer 1

That's because name is not a variable, it's a property in the window object. When you try to create a global variable named name, that will be ignored and the existing property will be used instead.

The type of the property is a string primitive, not a string object. The type of a variable is dynamic, so it could both hold a string primitive or a String object, but the property has a specific type and can only hold a string primitive.

typeof name will return "string", not "object". As it's not an object, it's not an instance of the String class.