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 function var 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 value var bar = foo.mapTo(10); bar.subscribe( function (x) { console.log(‘next ‘ + x); }, function (err) { console.log(‘error ‘ + err); }, function () { console.log(‘done‘); }, );
[RxJS] Transformation operator: map and mapTo
原文：http://www.cnblogs.com/Answer1215/p/5524725.html