Welcome to the Treehouse Community

The Treehouse Community is a meeting place for developers, designers, and programmers of all backgrounds and skill levels to get support. Collaborate here on code errors or bugs that you need feedback on, or asking for an extra set of eyes on your latest project. Join thousands of Treehouse students and alumni in the community today. (Note: Only Treehouse students can comment or ask questions, but non-students are welcome to browse our conversations.)

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and a supportive community. Start your free trial today.

JavaScript Object-Oriented JavaScript (2015) Introduction to Methods Finishing the Calculator


Implement the subtract method.

var calculator = {
  sum: 0,
  add: function(value) {
    this.sum += value;
  subtract: function(value) {

  multiply: function(value) {

  divide: function(value) {

  clear: function() {
    this.sum = 0;
  equals: function() {
    return this.sum;
    this.sum -= value;

1 Answer

Steven Parker
Steven Parker
220,378 Points

This might be easier than you think.

Take a look at the add method that has already been implemented. What the subtract method needs is very much like what is in the add method, but of course instead of adding (+) it will subtract ("-").

I'll bet you can do it now without an explicit spoiler.