Referring Javascript Instance Variable from Constructor without using 'this' keyword

Question

I'm just started with JavaScript oops concept , I want to access 3 instance variable from a constructor with out 'this' keyword, First value is coming but not 2nd.. and so on .. `

        function CreateObject()
        {
            var p1 = new person('chanky',25,'Male');           
        }

        function person(name,age,sex)
        {
            this.name = name; 
            this.age = age;
            this.sex = sex;      

            document.write(name); //Working
            document.write(age); //not Working
            document.write(sex); //not Working

         /*If we use 'this' keyword then all are Working */

            document.write(this.name); // Working
            document.write(this.age); // Working
            document.write(this.sex); // Working
        }`

when you are ommiting 'this' then you refer to argument of person function and with 'this' to instance property. you cannot mix these two to refer always to instance property — lukbl
– lukbl, Commented Jul 30, 2015 at 10:39
You don't refer instance variables, you refer constructor arguments (name,age,sex), this is not the same — hindmost
– hindmost, Commented Jul 30, 2015 at 10:40

Ricardo Pontual · Accepted Answer · 2015-07-30 10:46:57Z

What's the problem with 'this'? You want to access a member that you not declared, so you use 'this'.

You can access the values outside the class like this:

var p = new person('chanky',25,'Male');
alert (p.age);

function person(name,age,sex)
        {
            this.name = name; 
            this.age = age;
            this.sex = sex;      
        }

If you're still worried about, declare a variable and assign the values you've received to them, and as you're using an OO approach, encapsulate the variables to access them outside of your class

function person(name,age,sex)
        {
            var _name;
            var _age;
            var _sex;

            _name = name; 
            _age = age;
            _sex = sex;      

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

            this.getAge = function () {
                return _age;
            };

            this.getSex = function () {
                return _sex;
            };
        }

And use the 'methods':

var p2 = new person('chanky',25,'Male');
alert (p2.getAge());

Canvas · Accepted Answer · 2015-07-30 10:44:14Z

0

Hello there Chanky this should work fine

I have just created a jsFiddle to show using console.log

jsFiddle : https://jsfiddle.net/hq4ebs2d/

Javascript

function person(name, age, sex) {
    this.name = name;
    this.age = age;
    this.sex = sex;

    console.log(name); //Working
    console.log(age); //not Working
    console.log(sex); //not Working

    /*If we use 'this' keyword then all are Working */

    console.log(this.name); // Working
    console.log(this.age); // Working
    console.log(this.sex); // Working
};

var p1 = new person('chanky', 25, 'Male');

Just one quick note you have }` at the end of your code, make sure to change that to };

answered Jul 30, 2015 at 10:44

Canvas

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Comments

H77 · Accepted Answer · 2017-07-18 04:03:20Z

0

Please see the jsbin.. https://jsbin.com/teyupuhele/edit?html,js,output

This is best practice for OOP...

function person(name, age, sex) {
  this.name = name;
  this.age = age;
  this.sex = sex;


};

// create p1 instance of object person

var p1 = new person('chanky', 22, 'Male');

console.log(p1.name); //Working
console.log(p1.age); //Working
console.log(p1.sex); //Working

edited Jul 18, 2017 at 4:03

H77

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answered Jul 30, 2015 at 10:43

sag Surya

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