Finish Arrays section

Signed-off-by: Michael Tang <michael.h.tang@gmail.com>

expenses-tracker.js

@@ -0,0 +1,48 @@
+const account = {
+    name: 'Andrew Mead',
+    expenses: [],
+    income: [],
+    addExpense: function (description, amount) {
+        this.expenses.push({description, amount})
+    },
+    addIncome: function (description, amount) {
+        this.income.push({
+            description: description,
+            amount: amount
+        })
+    },
+    getAccountSummary: function () {
+        let total = 0
+        let totalIncome = 0
+        let totalExpenses = 0
+
+        this.expenses.forEach(function(expense) {
+            totalExpenses = totalExpenses + expense.amount
+        })
+        
+        this.income.forEach(function(income){
+            totalIncome = totalIncome + income.amount
+        })
+
+        total = totalIncome - totalExpenses
+
+        return `${this.name} has a balance of $${total}. $${totalIncome} in income. $${totalExpenses} in expenses.`
+    }  
+}
+
+// Expenses --> description, amount
+// addExpenses - description, amount
+
+// getAccountSummary - total up all expenses --> Andrew Mead has $1250 in expenses.
+
+// 1. add income arrray to account
+// 2. add income method -> description, amount 
+// 3. Tweak getAccountSummary 
+
+// Andrew Mead has a balance of $10. $100 in income. $90 in expenses. 
+account.addExpense('Rent', 950)
+account.addExpense('Coffee', 2)
+account.addIncome('Job', 1000)
+console.log(account.getAccountSummary())
+console.log(account.expenses)
+console.log(account.income)