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I am asking for good practices showing how to create a converting constructor in Javascript with the correct chain of prototypes.

It should: - get the existing object as a parameter - return a new class type object that contains all the properties of the old class - add new properties - change some of the properties

I want to avoid manually rewrite all properties.

If someone has a reference to examples of good practices creating other types of constructors and their inheritance, this can be helpful.

Right now working (but ugly) solution is here:

//Function from ( https://stackoverflow.com/questions/728360/how-do-i-correctly-clone-a-javascript-object )
function deepClone(obj)
{
        var copy;

        // Handle the 3 simple types, and null or undefined
        if (null == obj || "object" != typeof obj) return obj;

        // Handle Array
        if (obj instanceof Array) {
            copy = [];
            for (var i = 0, len = obj.length; i < len; i++) {
                copy[i] = deepClone(obj[i]);
            }
            return copy;
        }

        // Handle Object
        if (obj instanceof Object) {
            copy = {};
            for (var attr in obj) {
                if (obj.hasOwnProperty(attr)) copy[attr] = deepClone(obj[attr]);
            }
            return copy;
        }

        throw new Error("Unable to copy obj! Its type isn't supported.");
}



function A()
{
    this.param1 = {'a': 1};
    this.param2 = 'b';
}

A.prototype.getParam1 = function()
{
    return this.param1;
}

function B(objectToCopyFrom)
{

    //Code to copy all properties from the objectToCopyFrom and inherite prototype.
    Object.assign(this, deepClone(objectToCopyFrom));

    this.param1.a += 2;
    this.param3 = 'c';
}

B.prototype = Object.create(A.prototype);

B.prototype.getParam3 = function()
{
    return this.param3;
}

var a = new A();
a.param1 = {'a': 2};

var b = new B(a);

console.log(b.param3); //Should print: "c"
console.log(JSON.stringify( b.getParam1() )); //Should print: "{'a': 4}"

a.param1.a = 8;

console.log(JSON.stringify( b.getParam1() )); //Still should: "{'a': 4}"

https://jsfiddle.net/7h1gatom/6/

Please help me do it in a better, cleaner way without ES6 if it is possible.

Lukasz B
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  • Multiple inheritance can't really be implemented well https://stackoverflow.com/questions/9163341/multiple-inheritance-prototypes-in-javascript – CertainPerformance Jul 13 '19 at 08:37
  • Converting constructor do not need multiple inheritance. B can inherite from A (and A only). I'm just asking how to write proper constructor to do so, and handle parents object as a parameter (almost like a copy constructor). – Lukasz B Jul 15 '19 at 18:08

0 Answers0