将函数传递给Deferred的构造函数的优缺点

Question

In playing with Deferred's I see many different combinations of use. Most are the same, but occasionally I see ones that differ slightly.

FOR EXAMPLE...

NORMALLY, I SEE THIS :
Here we are merely using the Deferred.

// NORMALLY I SEE THIS...
function doSomething(){

    var deferred = $.Deferred();
    var myClass = new MyClass();

    myClass.doSomething(function () {
        deferred.resolve();
    });

    return deferred.promise();
};

OCCASSIONALLY, I SEE THIS:
Here we are passing a function into the Deferred's constructor...then using it.

// SOMETIMES I SEE THIS...
function doSomething() {

    var deferred = $.Deferred(function (deferred) {

        //Q: Is there an advantage to doing this instead?
        //Q: Is this a mis-use?
        var myClass = new MyClass();

        myClass.doSomething(function () {
            deferred.resolve();
        });
    });

    return deferred.promise();
};

MY QUESTION IS:

• Is there an advantage to doing the 2nd one instead?
• Is this a mis-use of the constructor?
• Does this practice create issue I just haven't seen yet?

I have yet to see any issue's arise from method 2. So, I'm looking for real insight here.

Answer 1

Is there an advantage to doing the 2nd one instead?

No, unless you enjoy callbacks which defeats the purpose of promises.

---

Is this a mis-use of the constructor?

Nope. jQuery deffered doc

jQuery.Deferred( [beforeStart ] )

 beforeStart Type: Function( Deferred deferred ) A function that is called just before the constructor returns. 

---

Does this practice create issue I just haven't seen yet?

No it doesn't, unless you intended to use myClass somewhere else which won't be possible since it is defined within your callback.

Conclusion:

In the end, it's more of a personal preference. Solution 1 just seems more clean to be honest.