promise sync vs async?

gistfile1.js

// Hey, what gives here? This is weird and unexpected.
// Why is the promise factory called synchronously, when
// all the other steps resolve async? For consistency,
// one would expect them all to be async.

var p = new Promise(function(resolve,reject){
   console.log("what");
   resolve();
});

p.then(function(){
   console.log("here?");
});

console.log("happened");

// got: what, happened, here?
// expected: happened, what, here?

Seems that is the norm. All the libraries listed here do the same.

http://www.promisejs.org/implementations/

edit: fixing some js typos

The trite/lame answer for "why is the promise constructor synchronous?" is "because the spec says so". Here's my guesses for the rationale behind the spec:

• Increased flexibility. Promises often perform async tasks but they don't necessarily need to do so.
• Safer initialization - the initializer may rely upon state that is altered in subsequent (synchronous)javascript statements. Consider the following (dumb) example:

var person = getPersonRecord();
var p = new Promise(function(resolve, reject){
    var grade = lookupStudentGrades(person.id);
    if(p.id) {
      displayGradeOnPage(grade);
      resolve();
    } else {
      reject();
    }
});
//... other statements...

person.id =  null;  

If the promise constructor was async, the promise would ultimately reject because one of the closures it uses was altered before the constructor had a chance to execute.