We made our first operator called multiplyBy, which looks a bit useful, but in practice we don't need it because it's too specific: it only does simple multiplication on numbers. In this lesson we will see how the map() operator is useful for any calculation on delivered values.

 

map:

var foo = Rx.Observable.interval(1000);/*foo: ---0---1---2---3--...       map(x => x / 2)bar: ---0---2---4---6--...*/// map take a functionvar bar = foo.map(x => x / 2);bar.subscribe(  function (x) { console.log('next ' + x); },  function (err) { console.log('error ' + err); },  function () { console.log('done'); },);

 

mapTo:

var foo = Rx.Observable.interval(1000);/*foo: --- 0---1--- 2--- 3--...       mapTo(10)bar: ---10---10---10---10--...*/// mapTo take a valuevar bar = foo.mapTo(10);bar.subscribe(  function (x) { console.log('next ' + x); },  function (err) { console.log('error ' + err); },  function () { console.log('done'); },);