Syntax Error, Or No Syntax Error?

var zero = 0; zero.toString(); // '0' --> fine 0.toString(); // syntax error! 0..toString(); // '0' --> fine My conclusion: calling x.toString() doesn't only depe

Solution 1:

Well, there are other cases where the context of where symbols appear affects how they behave, for example, statement Block's vs Object Literals:

{}          // empty blockvar o = {}; // empty object
({});       // empty object0,{}        // empty object

{ foo: 'bar'} // block, `foo` label, 'bar' ExpressionStatementvar o = { foo: 'bar'}; // object literal, declaring a `foo` property// whose value is 'bar'

They look exactly the same, but blocks are evaluates in "statement context", object literals are evaluated in expression context.

Also, Function Declarations vs. Function Statements, e.g.:

functionfoo() {}.length;   // SyntaxError, `foo` is a function declaration0,functionfoo() {}.length; // 0, `foo` is a function expression
(function foo {}).length;   // 0

The example you post, relates to the way the grammar of Numeric literals are defined, the decimal part after the dot is actually optional, for example:

var n = 0.;

Is a valid Numeric literal, that's why, accessing 0.toString gives you a SyntaxError, the interpreter would expect the decimal part, instead the s character.

See also:

• What does 1..something mean in JavaScript?

Solution 2:

The value of a variable doesn't matter, but the way it is "presented" might make it valid or invalid syntax. See this highly upvoted answer. It's just an oddity of the EcmaScript syntax definition.