Update README.md

README.md

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   prototypes are much more flexible in the sense that they may be mutable or immutable. The object
   may inherit from multiple prototypes, and only contains objects.
   ```
-
+
+  <a name="javascript--private-methods"></a><a name="6.6"></a>
+- **[6.7](#javascript--private-methods) What is the drawback of creating true private methods in JavaScript?**
+```javascript
+One of the drawbacks of creating true private methods in JavaScript is that they are very memory-inefficient, as a new copy of the method would be created for each instance.
+
+var Employee = function (name, company, salary) {
+    this.name = name || "";       //Public attribute default value is null
+    this.company = company || ""; //Public attribute default value is null
+    this.salary = salary || 5000; //Public attribute default value is null
+
+    // Private method
+    var increaseSalary = function () {
+        this.salary = this.salary + 1000;
+    };
+
+    // Public method
+    this.dispalyIncreasedSalary = function() {
+        increaseSlary();
+        console.log(this.salary);
+    };
+};
+
+// Create Employee class object
+var emp1 = new Employee("John","Pluto",3000);
+// Create Employee class object
+var emp2 = new Employee("Merry","Pluto",2000);
+// Create Employee class object
+var emp3 = new Employee("Ren","Pluto",2500);
+Here each instance variable emp1, emp2, emp3 has its own copy of the increaseSalary private method.
+
+So, as a recommendation, don’t use private methods unless it’s necessary.
+```
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