Why does 10..toString() work, but 10.toString() does not?
javascript, syntax
Solution
A `.` after a number might seem ambiguous. Is it a decimal or an object member operator?
However, the interpreter decides that it's a decimal, so you're missing the member operator.
It sees it as this:
(10.)toString(); // invalid syntax
When you include the second `.`, you have a decimal followed by the member operator.
(10.).toString();
@pedants and downvoters
The `.` character presents an ambiguity. It can be understood to be the member operator, or a decimal, depending on its placement. If there was no ambiguity, there would be no question to ask.
The specification's interpretation of the `.` character in that particular position is that it will be a decimal. This is defined by the numeric literal syntax of ECMAScript.
Just because the specification resolves the ambiguity for the JS interpreter, doesn't mean that the ambiguity of the `.` character doesn't exist at all.
Problem
Why does calling `152..toString(2)` return a binary string value of `"10011000"`, when a call to `152.toString(2)` throws the following exception? `"SyntaxError: identifier starts immediately after numeric literal"` It seems to me that it's intuitive to want to use the latter call to `toString()`, as it looks & feels correct. The first example just seems plain odd to me. Does anyone know why JavaScript was designed to behave like this?