Question

I remember reading in Douglas Crockford’s “Javascript the Good Parts” book that there is potential for error with blockless statements because of automatic semicolon insertion.

if (condition)
   foo = true;

vs

if (condition) 
{
   foo = true;
}

In the second the example it will work consistently, in the first example a semicolon will be automatically inserted by the interpreter and can lead to ambiguity in the code. As Douglas points out this is potentially bad and hard to debug, which I agree. But it got me thinking are there examples where coding “style” actually has syntax implications? In other words, examples where failing to follow a certain indentation or apparent style actually results in a bug or error. I suppose Python with its significant whitespace is an example, YML with its requirement for no tabs is another.

Feel free to respond in a wide variety of languages and idioms. I am curious to hear about the paradigm cases. In your answer I would like to know the WHAT and the WHY of the coding style or syntax behavior. I don’t want to start any coding style flame wars, just matter of fact scenarios where the uninitiated would get tripped up.

Answer 1

Javascript treats these two cases seperately. You have to use the first

return {
   // code
}

return 
{
   // code
}

If you do not the interpreter adds semi colons in the wrong places. I think it puts one after the condition. So the second would be read wrongly as.

return;
{
   // code
}

Which is not invalid syntax.