Finished Chapter 5.4 Object References

notes/chapter5_javascript-objects.md

@@ -20,3 +20,10 @@ Parse objects into function just like normal number, it allow us to parse multip
 
 Exmple check [object-function.js](../src/objects/objects-functions.js)
 
+## Object References
+
+When a object is parsed as argument into function, it's parsed as reference (not as a copy). Changes done by function on object affect original object
+
+But when a new value to the argument (in function), it break the binding (pass as reference) within function. But does not affect the original object
+
+Example check [object-references.js](../src/objects/objects-references.js)

src/objects/objects-references.js

@@ -0,0 +1,20 @@
+let myAccount = {
+    name: "Andrew Mead",
+    expenses: 0,
+    income: 0
+}
+
+let addExpense = function (account, amount) {
+    account.expenses = account.expenses + amount
+    console.log(account)
+}
+
+addExpense(myAccount, 2.5) // => { name: 'Andrew Mead', expenses: 2.5, income: 0 }
+addExpense(myAccount, 5.2) // =>  name: 'Andrew Mead', expenses: 7.7, income: 0 }
+
+addExpense = function (account, amount) {
+    account = {}
+    console.log(account) // => {} as it break binding
+}
+addExpense(myAccount, 2.5)
+console.log(myAccount) // => { name: 'Andrew Mead', expenses: 7.7, income: 0 }