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

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());

This could be interpreted as 42.0 without the trailing 0, then converting the integer to a string. — SPlatten, May 15 '17 at 10:35
The first dot is a decimal point, the second is the property accessor. This avoids parsing ambiguity between a member: 42.member and a mantissa: 42.123. — Alex K., May 15 '17 at 10:36
First dot is decimal point and second dot is for actual toString(). The Complier gets confused with single dot. — Jayakrishnan, May 15 '17 at 10:36
Although the question is quite different, [this answer](http://stackoverflow.com/a/4046367/1220550) explains quite well how to use it and why so. — Peter B, May 15 '17 at 10:39

score 12 · Accepted Answer · answered May 15 '17 at 10:36

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().

score 2 · Answer 2 · answered May 15 '17 at 10:38

2

it is like 42.0.tostring() so it show's decimal point you can use (42).toString() 42 .toString() that also work there is space between 42 and dot. This is all because in javascript almost everything is object so that confusion in dot opt.

answered May 15 '17 at 10:38

Afzal Patel

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Vivek Nerle · Answer 3 · 2017-05-15T12:13:51.033

1

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

edited May 15 '17 at 12:13

answered May 15 '17 at 11:05

Vivek Nerle

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2
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Why does a method like `toString` require two dots after a number?

3 Answers3