JavaScript 이외의 다른 언어가 중괄호 시작 위치 (같은 줄과 다음 줄)에 차이가 있습니까?

JavaScript 이외의 다른 언어가 중괄호 시작 위치 (같은 줄과 다음 줄)에 차이가 있습니까?

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오늘 저는 JavaScript patterns O'Reilly 책을 무작위로 읽는 동안 흥미로운 점을 발견했습니다 (참조 용 27 페이지).

Javascript에서는 경우에 따라 중괄호 시작 위치가 다르면 차이가 있습니다.

function test_function1() {
    return
    {
        name: 'rajat'
    };
}

var obj = test_function1();
alert(obj);  //Shows "undefined"

동안

function test_function2() {
    return {
        name: 'rajat'
    };
}

var obj = test_function2();
alert(obj); //Shows object

JSfiddle 데모

다른 언어에도 그러한 행동이 있습니까? 그렇다면 내 습관을 확실히 바꿔야 할 것 같다 .. :)

저는 주로 PHP, C, C ++, Java 및 루비에 관심이 있습니다.

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문을 구분하기 위해 세미콜론 (대신 개행)에 의존하지 않는 모든 언어는 잠재적으로이를 허용합니다. Python을 고려하십시오 .

>>> def foo():
...   return
...   { 1: 2 }
... 
>>> def bar():
...   return { 1: 2 }
... 
>>> foo()
>>> bar()
{1: 2}

Visual Basic 에서 비슷한 경우를 구성 할 수는 있지만 VB가 값을 배치 할 수있는 위치에있어 매우 제한적이기 때문에 어떻게해야하는지 알 수 없습니다. 그러나 정적 분석기가 도달 할 수없는 코드에 대해 불평하지 않는 한 다음은 작동합니다.

Try
    Throw New Exception()
Catch ex As Exception
    Throw ex.GetBaseException()
End Try

' versus

Try
    Throw New Exception()
Catch ex As Exception
    Throw
    ex.GetBaseException()
End Try

언급 한 언어에서 Ruby 는 동일한 속성을 가지고 있습니다. PHP, C, C ++ 및 Java는 단순히 줄 바꿈을 공백으로 버리고 명령문을 구분하기 위해 세미콜론을 필요로하기 때문이 아닙니다.

다음은 Ruby의 Python 예제에 해당하는 코드입니다.

>> def foo
>>   return { 1 => 2 }
>> end
=> nil
>> def bar
>>   return
>>   { 1 => 2 }
>> end
=> nil
>> foo
=> {1=>2}
>> bar
=> nil

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JavaScript 인터프리터는 자동으로 ;각 줄 끝에를 추가합니다 (일부 예외는 있지만 여기에 들어 가지 않습니다 :).

So basically the issue is not the braces' location (which here represent an object literal, not a code block as in most languages), but this little "feature" that forces your first example to return ; => undefined. You can check out the behavior of return in the ES5 spec.

For other languages that have similar behavior, check out Konrad's answer.

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Most certainly. Google's go programming language exhibits a very similar behavior (albeit with different effects). As explained there:

In fact, what happens is that the formal language uses semicolons, much as in C or Java, but they are inserted automatically at the end of every line that looks like the end of a statement. You don't need to type them yourself.

..snip...

This approach makes for clean-looking, semicolon-free code. The one surprise is that it's important to put the opening brace of a construct such as an if statement on the same line as the if; if you don't, there are situations that may not compile or may give the wrong result. The language forces the brace style to some extent.

Secretly, I think Rob Pike just wanted an excuse to require the One True Brace Style.

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The answer to that question is fairly easy. Any language that has "automatic semicolon insertion" might be in trouble on that line. The problem with this

return
{
     name: 'rajat'
};

..is that the js engine will insert a semicolon after the return; statement (and therefore, return undefined). This example is a good reason to open curly brackets always on the right side and never on the left side also. Since you already correctly noticed, if there is a curly bracket in the same line, the interpretator will notice that and can't insert a semicolon.

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FWIW, JSLint reports several warnings with that syntax:

$ jslint -stdin
function foo(){
  return
  { x: "y" };
}
^D
(3): lint warning: unexpected end of line; it is ambiguous whether these lines are part of the same statement
  return
........^

(3): lint warning: missing semicolon
  { x: "y" };
..^

(3): lint warning: unreachable code
  { x: "y" };
..^

(3): lint warning: meaningless block; curly braces have no impact
  { x: "y" };
..^

(3): lint warning: use of label
  { x: "y" };
.....^

(3): lint warning: missing semicolon
  { x: "y" };
...........^

(3): lint warning: empty statement or extra semicolon
  { x: "y" };
............^


0 error(s), 7 warning(s)

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The first language where I came across this was awk (which also has its share of syntax "oddities"; optional semi colons, string concatenation using only whitespace and so on...) I think the DTrace designers, which based the D syntax loosely on awk, had enough sense to NOT copy these features, but I can't remember off the top of my head. A simple example (counting the number of ENTITY tags in a DTD, from my Mac):

$ cat printEntities.awk 
# This prints all lines where the string ENTITY occurs
/ENTITY/ {
  print $0
}
$ awk -f printEntities.awk < /usr/share/texinfo/texinfo.dtd | wc -l
     119

If this little script instead were written with the brace on a line of its own, this is what would happen:

$ cat printAll.awk 
# Because of the brace placement, the print statement will be executed
# for all lines in the input file
# Lines containing the string ENTITY will be printed twice,
# because print is the default action, if no other action is specified
/ENTITY/
{ 
   print $0 
}
$ awk -f printAll.awk < /usr/share/texinfo/texinfo.dtd | wc -l
     603
$ /bin/cat < /usr/share/texinfo/texinfo.dtd | wc -l
     484
$ 

참고URL : https://stackoverflow.com/questions/9191776/does-any-other-language-other-than-javascript-have-a-difference-between-brace-st