Why does a primitive variable act like an Object? [duplicate]

Answer 1

The primitive type Number has a corresponding object representation, which you can create with new Number. This is an object and is therefore of a different data type than the primitive type Number.

If you call Number(34) (without new) an object isn't created, but the Number function performs a type conversion, to a primitive number value.

var num1 = new Number(34); // object
var num2 = 34; // primitive

When you call sayMyNumber() on the primitive number num2, JavaScript internally converts the primitive temporarily to its equivalent object version. And because you added sayMyNumber() to Number.prototype you have access to the function.

The reason 34.sayMyNumber() doesn't work is because when JavaScript engine parses your source code, it has to interpret just what a dot means in a given context. In the case of 34.sayMyNumber() the dot is potentially ambiguous. Does it mean the decimal separator? Or does it mean object member access? JavaScript opts to interpret all integers followed by a dot as representing part of a floating point number. But as there is no such number 34.sayMyNumber(), it raises a SyntaxError. Read more here

Answer 2

JavaScript coerces between primitives and objects. In this case the number value is coerced to a Number object in order to access the prototype method sayMyNumber. Actually, in this way primitives have access to all the properties and methods defined by their respective object constructors. However, they are different from the objects as they are immutable.

Thus, (34).sayMyNumber(); works; so does (34).toFixed() or (34).toPrecision().

As for 34.sayMyNumber();, as hindmost pointed out, is a syntax error.

Answer 3

For both,

var num1 = new Number(34); 
num2 = 34;

You are assigning "Number" type values to both num1 and num2 variables. So it calls the prototype, which attached to the "Number".

But calling 34.sayMyNumber has syntax error and its an illegal statement.

If anyone has question on this please refer... https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number