Make another Method Calc

Making a calculator isn't so hard.  Lets take a look.

var calculator = {
    sum: 0,
    add: function(value) {
    this.sum += value;
  },
    subtract: function(value) {
    this.sum -= value;
  },
    multiply: function(value) {
    this.sum = this.sum * value;
  },
    divide: function(value) {
    this.sum = this.sum / value;
  },
    clear: function() {
    this.sum = 0;
  },
    equals: function() {
    return this.sum;
  }
}