typescript - Getting a number from KO observable -

(i sorry many typescript questions - getting started ts)

i have ko observable called index. want increase value of one.

original js code:

data.index(data.index()+1);

this gives compile error: left hand side must number... value number.

var currentindex: number = data.index(); data.index(currentindex-1);

however, compile error: type '{}' not assignable type 'number'.

how tell ts index() returning number?

a knockout observable containing number can defined so:

var myobservable : knockoutobservable<number>;

you should specify type observable contain. example:

var data = {     index : ko.observable<number>(),     // etc.. };

that way when call data.index() compiler knows returned type number:

data.index(data.index() + 1); // ok

Call