//emit array as a sequence

const source = Rx.Observable.from([1,2,3,4,5]);

​

//let provides flexibility to add multiple operators to source observable then return

const subscribeTwo = source

   .map(val => val + 1)

   .let(obs => obs

      .map(val => val + 2)

      //also, just return evens

      .filter(val => val % 2 === 0)

    )

  //output: 4,6,8

  .subscribe(val => console.log('let WITH MULTIPLE OPERATORS: ', val));