Question

I want extend a new JS object while creation with other object passing a parameter.
This code does not work, because I only can extend object without dynamic parameter.

otherObject = function(id1){
    this.id = id1;
};

otherObject.prototype.test =function(){
    alert(this.id);
};

testObject = function(id2) {
    this.id=id2;
};

testObject.prototype = new otherObject("id2");/* id2 should be testObject this.id */


var a = new testObject("variable");
a.test();

Any suggestion?

Answer 1

Apart from the obvious syntax error, the correct JavaScript way of inheritance is this:

// constructors are named uppercase by convention
function OtherObject(id1) {
    this.id = id1;
};
OtherObject.prototype.test = function() {
    alert(this.id);
};

function TestObject(id2) {
    // call "super" constructor on this object:
    OtherObject.call(this, id2);
};
// create a prototype object inheriting from the other one
TestObject.prototype = Object.create(OtherObject.prototype);
// if you want them to be equal (share all methods), you can simply use
TestObject.prototype = OtherObject.prototype;


var a = new TestObject("variable");
a.test(); // alerts "variable"

You will find lots of tutorials about this on the web.