problem1.js

console.clear();

// Get elements
var weightSliderElem = document.querySelector('#weight-slider');
var weightTextElem = document.querySelector('#weight-text');
var heightSliderElem = document.querySelector('#height-slider');
var heightEditTextElem = document.querySelector('#height-edit-text');
var heightTextElem = document.querySelector('#height-text');
var bmiTextElem = document.querySelector('#bmi-text');

// Observables
var weight = Rx.Observable.fromEvent(weightSliderElem, 'input')
  .map(ev => ev.target.value)
  .startWith(weightSliderElem.value);

var height1 = Rx.Observable.fromEvent(heightSliderElem, 'input')
  .map(ev => ev.target.value)
  .startWith(heightSliderElem.value);

var height2 = Rx.Observable.fromEvent(heightEditTextElem, 'input')
  .map(ev => parseInt(ev.target.value))
  .startWith(heightEditTextElem.value);

// TODO: create the Observable `bmi` which depends on
// Observables `weight` AND [`height1` OR `height2`].

// Subscriptions
weight.subscribe(x => weightTextElem.innerHTML = x);
height1.subscribe(x => heightTextElem.innerHTML = x);
bmi.subscribe(x => bmiTextElem.innerHTML = x);