Rx.Observable.prototype.select(selector, [thisArg])Projects each element of an observable sequence into a new form by incorporating the element’s index. This is an alias for the map method.
selector (Function): Transform function to apply to each source element. The selector is called with the following information:
[thisArg] (Any): Object to use as this when executing the predicate.(Observable): An observable sequence which results from the comonadic bind operation.