toString only works with parenthesis or non-literal numbers

Question

For some reason, when I try to call toString on a literal number, it fails:

> 5.toString()
SyntaxError: Unexpected token ILLEGAL

So I tried putting it in a variable, and it worked:

> var five = 5
undefined
> five.toString()
"5"

I thought that was a bit strange, and after some more experimenting, I found out that wrapping a literal in parenthesis somehow makes it work:

> (5).toString()
"5"

That seemed very strange! Why would wrapping the literal in parenthesis change anything? Why does 5.toString() not work?

@Musa Oh thanks, I didn't find that because I thought it had to do with `toString` and not calling methods on numbers :P — tckmn, May 20 '13 at 22:42

GriffLab · Accepted Answer · 2013-05-20T22:46:34.327

8

The dot . after the number represents a decimal point.

It would work if you do;

5..toString();

To clarify when a decimal point is followed by a number in javascript it expects the next character to be that of a number, so if toString() is there instead it is considered an illegal token as t is not a valid number.

This is another valid way of doing the same thing but is easier to read and follow;

5.0.toString();

edited May 20 '13 at 22:46

answered May 20 '13 at 22:41

GriffLab

2,076
3
20
21

That's strange. Thanks! I can accept the answer in 7 minutes – tckmn May 20 '13 at 22:44
I added an explaination for you, – GriffLab May 20 '13 at 22:46

score 2 · Answer 2 · answered May 20 '13 at 22:41

Why would wrapping the literal in parenthesis change anything?

This causes the literal to become an expression. As a result, you can call the method .toString() on the expression. As linked by @Musa, the . after a number is interpreted as a decimal point causing an exception to be thrown when 5.t is encountered as t is not a valid number.

toString only works with parenthesis or non-literal numbers

2 Answers2