why does 1..toString() work and return "1" but 1.toSring() cause an syntax error?

Question

I know 1 is not an object, but when I type 1..toString(), it returns "1" in the console. Why is that?

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It's a frequent question, let's look for the proper QA for closing... — Denys Séguret, Jan 04 '17 at 16:18
This question has a lot of good explanations: http://stackoverflow.com/questions/4211037/what-is-the-double-dot-operator-in-javascript — Johnny Kutnowski, Jan 04 '17 at 16:19
1..toString is not the double dot operator: http://stackoverflow.com/a/4211641/735926 — bfontaine, Jan 04 '17 at 16:20
If the question is why you can access properties on primitive values, see [Does javascript autobox?](http://stackoverflow.com/q/17216847/218196) — Felix Kling, Jan 04 '17 at 16:23
@Mouser - If that was true, you wouldn't be able to add numbers as it would do string concatenation. — Loaf, Jan 04 '17 at 16:24
@leo_ap Anyone who writes `1 .toString()` rather than `'1'` deserves to have errors. — Dan Prince, Jan 04 '17 at 16:28

score 6 · Answer 1 · answered Jan 04 '17 at 16:18

6

Because the JavaScript parser assumes that 1. must be followed only by one or more digits to represent a float number. Using parentheses works: (1).toString().

answered Jan 04 '17 at 16:18

bfontaine

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score 1 · Answer 2 · answered Jan 04 '17 at 16:20

1

Because it is interpreting 1. as the number. When you have 1.toString(), it is the same as saying (1.)toString(). Therefore 1..toString() is the same as (1.).toString()

answered Jan 04 '17 at 16:20

Loaf

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score 0 · Answer 3 · answered Jan 04 '17 at 16:17

The reason why the below works is:

1..toString()

The 1.. is considered as a floating point number. The console expects something like:

1.0
1.5

Or something. If you are giving something like:

1.toString();

The above is not a valid number. That's the reason. So to make the above work, you need a parenthesis to tell that the number is completed:

(1).toString();

why does 1..toString() work and return "1" but 1.toSring() cause an syntax error?

3 Answers3