We have the following code:
function Order() {
this.orderLines = [];
this.orderTotal = 0;
}
Order.prototype.getOrderLines = function() {
return this.orderLines;
};
Order.prototype.addOrderLine = function(orderLine) {
this.orderTotal += orderLine.total;
this.orderLines.push(orderLine);
};
Order.prototype.removeOrderLine = function(orderLineItem) {
var orderTotal, orderLine;
orderLine = this.orderLines.map(function(order) {
return order === orderLineItem;
})[0];
if(typeof orderLine === 'undefined' || orderLine === null) {
return;
}
this.orderTotal -= orderLine.total;
this.orderLines.splice(this.orderTotal, 1);
};
var order = new Order();
order.addOrderLine( { total: 10 } );
console.log(order.getOrderLines()); // [ { total: 10 } ]
console.log(order.orderTotal); // 10
The problem with this code is that anyone could get access to orderLines and add or modify values without increasing or decreasing orderTotal.
order.orderLines[0] = { total: 20 };
console.log(order.getOrderLines()); // [ { total: 20 } ]
console.log(order.orderTotal); // 10;
function Order() {
var orderLines, orderTotal;
orderLines = [];
orderTotal = 0;
this.getOrderLines = function () {
return orderLines;
};
this.getOrderTotal = function () {
return orderTotal;
};
this.setOrderTotal = function (total) {
orderTotal += total;
};
}
Order.prototype.addOrderLine = function (orderLine) {
var orderLines;
orderLines = this.getOrderLines();
this.setOrderTotal(orderLine.total);
orderLines.push(orderLine);
};
Order.prototype.removeOrderLine = function(orderLineItem) {
var orderTotal, orderLine, orderLines;
orderLines = this.getOrderLines();
orderLine = this.orderLines.map(function(order) {
return order === orderLineItem;
})[0];
if(typeof orderLine === 'undefined' || orderLine === null) {
return;
}
this.setOrderTotal( (-1 * orderLine.total) );
orderLines.splice( this.getOrderTotal(), 1);
};
var order = new Order(); assert(typeof order.orderLines === 'undefined');