Concise syntax for javascript if statements without curly brackets

Question

So pragmatically, I\'ve got a quick and dirty answer to what I\'m looking for here. But why isn\'t using that a good idea? Why can\'t I find any formal documentation of it

Answer 1

why isn't using that a good idea?

It is far to easy to add another statement and expect it to only fire if the if passes

Why can't I find any formal documentation of it?

The MDN documentation:

Statement that is executed if condition evaluates to true. Can be any statement, including further nested if statements. To execute multiple statements, use a block statement ({ ... }) to group those statements.

ECMA-262 (page 89):

if ( Expression ) Statement

It seems that there's an indentation based one

No. Just an if, then a condition, then a statement. The statement can be formatted on the same line or the next line.

White space is not significant in JS.

Answer 2

But why isn't using that a good idea?

Because it's hard to maintain.

Why can't I find any formal documentation of it? Is it not part of the spec and standard?

Of course it is, see §12.5 - The if Statement and §12 - Statements in the spec. The body of an if is a Statement. One kind of Statement is Block (§12.1), which allows a list of statements to be treated as one statement, but there are many other kinds of statements.

Is it not widely supported?

Universally.

Is it just because minification could break code using that syntax?

A good minifier won't break that syntax. (A good minifier will make use of it, in fact.)

What defines the contents of the if block? Is it indentation based?

The body of an if statement consists only of the statement following it, indentation has no significance in JavaScript. So all of these are equivalent:

if (foo)
    bar();
charlie();

if (foo) bar();
charlie();

if (foo)
bar(); charlie();

    if (foo)
bar();
    charlie();

In the above, only the call to bar is conditional on foo; charlie is called regardless.

That's why we have Block, the Statement that introduces a list of statements to be treated as a unit (a block, you might say :-) ):

if (foo) {
    bar();
}
charlie();

if (foo) { bar(); }
charlie();

if (foo) {
bar(); } charlie();

    if (foo)
{ bar(); }
    charlie();

Indentation is important for humans, though, so keeping consistent indentation is a good idea. The first example in each of the above is probably clearest (of the ones listed) for us mere mortals. :-)

On another note, is there something similar to this syntax for if statements in PHP?

I'm not a big PHP-head, but it looks identical, defined in Control Structures - if. There are examples with and without {}. (There's also a different, alternative syntax I won't go into here.)

Does such an if block support having an else as well, both in JS and PHP?

Yes, if supports else both with and without blocks.

Answer 3

The statement following an if is just that: a statement.

One of the possible forms a statement can take is that of a brace-enclosed group of statements.

Thus, the syntax of an if statement is

if ( expression ) statement

Thus the reason that braces improve maintainability is that they provide an explicit boundary to the scope of influence of the if control flow effect.

Answer 4

It is standard, part of the spec (if-statement, other statements) and supported everywhere. Minification does not break it, because whitespaces have no semantics in JS - it even will enforce it for one-line-statements to save the two braces.

So, it is widely used (without problems!) as well. Sometimes it is considered bad because appending statements to the indented body without adding the braces can lead to problems. Also, it can lead to erratic behaviour when used in nested ifs:

if (false)
    if (whatever)
         ;
else
    alert("");

Would you have expected an alert? No, the else belongs to the last if.

Yet, you can use it unconcerned for one-line-statements that are sure not to get extended, like return;.

Answer 5

javascript is not white space sensitive, meaning

if(condition) do_some_statement();

is the same as

if(condition)
    do_some_statement();

that being said, omitting braces in a single line if statement is always frowned upon because it can lead to bugs if the if statement ever needs to be modified:

if(condition)
    do_some_statement();
    // someone adds another line here, without adding the braces
    // now you've introduced a bug

also, is it really that hard to write { }? :P