Difference between unwrapObservable and ()

问题:

Is there an actual difference between:

y = ko.observable("value");
x = ko.utils.unwrapObservable(y);

and:

y = ko.observable("value");
x = y();

Should I prefer one of the above and why?

回答1:

The difference is that ko.utils.unwrapObservable is safe. You should use it when don't know if parameter is observable or not. For example:

function GetValue(x){
   return ko.utils.unwrapObservable(x);
}

function GetValueEx(x){
   return x();
}

var test = 5;
var y = GetValue(test) // Work fine, y = 5;
y = GetValueEx(test) // Error!

So if you exactly know that your parameter is observable you can use () otherwise use unwrapObservable.

EDIT: A shorter version of unwrapObservable has been added in knockout 2.3 - ko.unwrap