Question

What are the parsing rules regarding the debugger keyword?

On Chrome, the following works fine:

debugger
console.log('Hello!')

but

debugger console.log('Hello!')

is a SyntaxError.

Why is replacing one form of whitespace (new line) by another form of whitespace (space) so critical? What are the parsing rules for debugger?

Answer 1

This is not related to the debugger statement at all, it’s down to automatic semi-colon insertion.

It’s the same as trying

alert('Hi');
console.log('Hello');

and

alert('Hi') console.log('Hello');

Automatic semi-colon insertion is turning your input into;

debugger;
console.log('Hello!');