Classical Inheritance in JavaScript : Reassigning the constructor

Question

I am trying to learn inheritance in JavaScript using prototype keyword.

I came a code across a web-site which explained me classical inheritance in JavaScript. I am using Mozilla Rhino for command-line javaScript

This is my code

    var fn55 = function(){

    var Employee = function(name){

        var name = name;

        this.getName = function(){
            return name;
        };

        this.setName = function(empName){
            name = empName;
        };  
    };

    var ContractEmp = function(name,sal){
        var salary = sal;

        this.getSalary = function(){
            return salary;
        }
        //calling super constructor
        Employee.apply(this,[name]);            
    };
    ContractEmp.prototype = new Employee();
    ContractEmp.prototype.constructor = ContractEmp;


    var emp1 = new ContractEmp("Jack",3000);
    var emp2 = new ContractEmp("John",4000);
    print(emp1.getName());
    print(emp2.getName());
    print(emp1.getName());

    Employee.prototype.getInfo = function(){
        return "Emp Name \""+this.getName()+"\" Salary "+this.getSalary();
    }

    print(emp1.getInfo());
};

fn55();

the output is

Jack
John
Jack
Emp Name "Jack" Salary 3000

Now if I comment a line in my code

//ContractEmp.prototype.constructor = ContractEmp;

the output remains as it is.

So my question is, whats the purpose of this re-assigning the constructor

I believe this is due to some ancient IE behavior, never reassigned the constructor and never bit me :-) — mfeineis, Jun 01 '15 at 07:26
It is not necessary to assign a constructor to a prototype object, but it can be helpful under circumstances. Then `myObject.constructor` can be used to access an object's constructor at runtime. — GOTO 0, Jun 01 '15 at 07:34

score 0 · Accepted Answer · edited May 23 '17 at 12:22

0

So my question is, whats the purpose of this re-assigning the constructor

The only purpose is to reset constructor to its original value.

See also What it the significance of the Javascript constructor property?

edited May 23 '17 at 12:22

Community

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answered Jun 05 '15 at 16:03

Felix Kling

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Classical Inheritance in JavaScript : Reassigning the constructor

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