javascriptでreturn functionとreturn function()の違い

参照https://stackoverflow.com/questions/7629891/functions-that-return-a-function-javascript
 
 
問題:唯一の違いは、リセットの関数が括弧を持つかどうかです.
入力:

function a() {

    alert('A!');

    function b(){
        alert('B!'); 
    }

    return b();
}

var s = a();
alert('break');
s();

 
出力:

A!
B!
break

 
 
入力:

function a() {

    alert('A!');

    function b(){
        alert('B!'); 
    }

    return b;
}

var s = a();
alert('break');
s();

 
出力:

A!
break
B!

 
回答1:
 
Asigning a variable to a function(without the parenthe sis)copies the reference to the function.Puting the parenthe the sis the the end of a function name、cars the function、returning the functions return value.
 
 
http://jsfiddle.net/kaleb/Las6w/

function a() {
    alert('A');// A        
}
//alerts 'A', returns undefined

function b() {
    alert('B');
    return a; //        
}
//alerts 'B', returns function a

function c() {
    alert('C');
    return a();//        
}
//alerts 'C', alerts 'A', returns undefined

alert("Function 'a' returns " + a());
alert("Function 'b' returns " + b());
alert("Function 'c' returns " + c());

回答2:
 
Returning the function name without  () returns a reference to the function,which can be as you've done with  var s = a().  s now contains a reference to the function  b()、andカリン  s() is functionlly equivalent to caling  b().

// Return a reference to the function b().
// In your example, the reference is assigned to var s
return b;

 
Calling the function with  () in a return statement executes the function,and returns whatever value was returned by the function.It is simiar to caling  var x = b();、but instead of assigning the return value of  b() you are returning it from the call ling function  a().If the function  b() itself does not return a value,the call returns  undefined after whatever other work is done by  b().

    
Returning the function name without () returns a reference to the function, which can be assigned as you've done with var s = a(). s now contains a reference to the function b(), and calling s() is functionally equivalent to calling b().

// Return a reference to the function b().
// In your example, the reference is assigned to var s
return b;
Calling the function with () in a return statement executes the function, and returns whatever value was returned by the function. It is similar to calling var x = b();, but instead of assigning the return value of b() you are returning it from the calling function a(). If the function b() itself does not return a value, the call returns undefined after whatever other work is done by b().

// Execute function b() and return its value
return b();
// If b() has no return value, this is equivalent to calling b(), followed by
// return undefined;

 回答3:
  return b(); cals the function b()、and returns its reult.return b; returns a reference to the function b,which you can store in a variable to call later.