Why does a method like `toString` require two dots after a number? [duplicate]

Question

What is the logic behind 42..toString() with ..?

The double dot works and returns the string "42", whereas 42.toString() with a single dot fails.

Similarly, 42...toString() with three dots also fails.

Can anyone explain this behavior?

console.log(42..toString());

console.log(42.toString());

Answer 1

When you enter 42.toString() it will be parsed as 42 with decimal value "toString()" which is of course illegal. 42..toString() is simply a short version of 42.0.toString() which is fine. To get the first one to work you can simply put paranthesis around it (42).toString().

Answer 2

With just 42.toString(); it's trying to parse as a number with a decimal, and it fails.

and when we write 42..toString(); taken as 42.0.toString();

we can get correct output by

(42).toString();

(42.).toString();

Can refer Link for .toString() usage