CODEWITHSUNDEEP
javascriptinheritanceprototype
Gopal
Gopal

Reputation: 1340

Prototypal Inheritence in Javascript

How to pass values to super class constructors in Javascript.

In the following code snippet

(function wrapper() {
var id = 0;

window.TestClass = TestClass;

function TestClass() {
    id++;
    this.name = 'name_' + id;
    function privateFunc() {
        console.log(name);
    }
    function publicFunc() {
        privateFunc();
    }

    this.publicFunc = publicFunc;
}

function TestString() {
    this.getName = function() {
        console.log("***" + this.name + "****************");
    }
}

TestClass.prototype = new TestString(); 
})();

How do I pass values to the TestString constructor? Currently, the super class method is using value using 'this' keyword. Is there a way to directly pass values to the super class constructor. Also, I want to see a simple example of extending String. That would demystify a lot of things.

Upvotes: 0

Views: 96

Answers (1)

alex
alex

Reputation: 490233

You can use the following code in the constructor of TestClass().

TestString.apply(this, arguments);

This will call the constructor with the new object as its context.

However, note that establishing the [[Prototype]] chain with TestClass.prototype = new TestString(); will have already called the constructor once.

jsFiddle.

I want to see a simple example of extending String.

You can augment its prototype property.

String.prototype.endsWidth = function(str) {
    return this.slice(-str.length) === str;
};

Upvotes: 2

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