Relying on short-circuit evaluation instead of using the IF control structure [closed]

Question

Examples of where I've started migrating to short-circuit evaluation:

PHP

$id=0;//initialized in case of no result
$r=mysql_query(SQL);
if($r && mysql_num_rows($r)>0){
  list($id)=mysql_fetch_row($r);
}

becomes

$id=0;
$r=mysql_query(SQL);
$r && mysql_num_rows($r)>0 && list($id)=mysql_fetch_row($r);

JavaScript

var Req=jQuery.ajax(OBJECT);
//Something has happened and now i want to abort if possible
if(Req && Req.abort){
  Req.abort();
}

becomes

var Req=jQuery.ajax(OBJECT);
//Something has happened and now i want to abort if possible
Req && Req.abort && Req.abort();

I'm familiar with the short if style of

if(Req && Req.abort) Req.abort();

but it feels clunkier than short-circuit evaluation.

Answer 1

This is an abuse of short-circuit evaluation. It's not immediately obvious what the intent is. Sure, i can eventually see that you're getting an ID, calling Req.abort(), whatever. But i shouldn't have to decipher a line of code first to figure out what it does. Conciseness never trumps readability in source code. (Sure, minifying/packing JS has its benefits. But you don't write packed/minified code; you start out with decent code and then run a tool on it.)

Since your intent is to do the one thing if the other stuff is true, the code should say that.

Answer 2

Also, jsbeautifier will format your code like this:

var Req = jQuery.ajax(OBJECT);  //<- Note the spaces around the equal sign
//Something has happened and now i want to abort if possible
if(Req && Req.abort)
{
  Req.abort();
}

Beyond, that lowerCamelCase should apply so Req -> req or even better request and OBJECT -> object, I am not too excited about either generic name, but I guess this is just a stub.

Furthermore it seems a bit paranoid to not trust request or request.abort(), I don't have enough code to see if this paranoia is justified.

Personally, I have taken to write this as :

( request && request.abort ) ? request.abort() : undefined;

or, with jQuery providing noop

( request && request.abort ) ? request.abort() : $.noop();

The undefined yells at my subconscious that I should really handle request or request.abort being falsey.

Furthermore, on if statements with 1 statement in the true block

Not acceptable:

if(Req && Req.abort) Req.abort();

Somewhat acceptable:

if(Req && Req.abort) 
  Req.abort();

Best practice:

if(Req && Req.abort){
  Req.abort();
}