his.dataProvider.getProducts().subscribe((products) => {
      this.products = products;

  //Pull an Array of ASINs from Firebase Database
  this.products.forEach(product => {
  this.asins.push(product.ASIN)

  this.productKey.push(product.$key)
  //console.log(this.productKey.toString());
  var lastASIN = this.productKey.pop();
  console.log (lastASIN);

    return this.dataProvider.getNextProducts(lastASIN).subscribe((products) => {
      this.products.forEach(product => {
        this.asins.push(product.ASIN)
        this.productKey.push(product.$key)
        var newASIN = this.productKey.pop();
        console.log (newASIN);
      })
    })

  });

import 'rxjs/add/operator/take';
import 'rxjs/add/operator/skip';

this.dataProvider.getNextProducts(lastASIN).skip(numToSkip).take(10).subscribe(...

new Firebase("https://examples-sql-queries.firebaseio.com/widget")
   .startAt(null, lastWidgetOnPrevPage)
   .limitToFirst(LIMIT+1) // add one to limit to account for lastWidgetOnPrevPage
   .once('value', function(snap) {
      var vals = snap.val()||{};
      delete vals[lastWidgetOnPrevPage]; // delete the extraneous record
      console.log('widgets on this page', vals);
   });