CODEWITHSUNDEEP
javascript
cgsd
cgsd

Reputation: 1323

Why can you call toString() on an integer variable but not a literal number?

How come this works:

var num = 1;
console.log(num.toString()); // "1"

But this does not?

console.log(1.toString()); // SyntaxError: Unexpected token ILLEGAL

Upvotes: 2

Views: 123

Answers (1)

James Allardice
James Allardice

Reputation: 166021

Because the grammar expects a . after a number to be parsed as part of that number, as it would be for e.g. 1.5. You need to disambiguate the . if you want to use it as a member operator on a numeric literal:

1..toString();  // "1"
1.0.toString(); // "1"
(1).toString(); // "1"

In the first two cases the first . is parsed as a floating point. The second can only be parsed as a member operator because numeric literals can only contain a single floating point.

This is shown by the NumericLiteral grammar in the spec.

Upvotes: 8

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