In Processing web service data, Why m.prop is not required? - mithril.js

Question

Note that this getter-setter holds an undefined value until the AJAX
request completes.
var users = m.prop([]); //default value
var doSomething = function() { /*...*/ }
m.request({method: "GET", url: "/user"}).then(users).then(doSomething)
But following code is not used m.prop. Why?
Are you set the default value in a different way?
//model
var User = {}
User.listEven = function() {
return m.request({method: "GET", url: "/user"}).then(function(list) {
return list.filter(function(user) {return user.id % 2 == 0});
});
}
//controller
var controller = function() {
return {users: User.listEven()}
}
If ok in the above code, and useless in the following?
var doSomething = function() { /*...*/ }
m.request({method: "GET", url: "/user"}).then(doSomething)
https://lhorie.github.io/mithril/mithril.request.html

Answer 1

The listEven code works because both m.prop and m.request returns a GetterSetter, but when using m.request the GetterSetter will be populated with the value returned from the promise. It's quite convenient.
And in the last example there is no GetterSetter involved, it's a simple promise usage. So all three examples works fine. To decide which one is best, you have to look at your specific case.