duplicate constructor function

Question

How to reuse the same constructor function in multiple objects?

Here creditor_group is constructed in both objects.. How to duplicate the Delegate function!?

code

var App = {};
App.module_group = function(main, location, table){
    this.init = function(){
        console.log('init: '+table+' args: '+main+', '+location);
    };
    
    this.test = function(){
        console.log('test: '+table);
    };
};

function Delegate(main, location){
    this.table;
    this.module_name;
    
    var module;
    
    this.init = function(){
        module = new App[this.module_name](main, location, this.table);
        module.init();
        
        return module;
    };
    
    this.test = function(){
        module.test();
    };
}

var module_1 = Delegate;
module_1.prototype.table = 'debtor_group';
module_1.prototype.module_name = 'module_group';

var module_2 = Delegate;
module_2.prototype.table = 'creditor_group';
module_2.prototype.module_name = 'module_group';

// This part where the objects are constructed is done in another scope
var m_1 = new module_1('main', 'location');
m_1.init();
m_1.test();
var m_2 = new module_2('main', 'location');
m_2.init();
m_2.test();

console

init: creditor_group args: main, location
test: creditor_group
init: creditor_group args: main, location
test: creditor_group

The console output happens because both module_1.prototype and module_2.prototype refer to the same object, so you overwrite the table property. — CrowbarKZ
– CrowbarKZ, Commented Feb 20, 2015 at 11:59
It is a bit unclear to me what you want to do there. If you want to create different objects with the same constructor, you can pass all the values (e.g. table, module_name) as parameters. Or you can create new constructors which inherit from Delegate and change their prototypes. — CrowbarKZ
– CrowbarKZ, Commented Feb 20, 2015 at 12:10

Bergi · Accepted Answer · 2015-02-20 12:07:42Z

2

Sounds like you want to use inheritance with two extra constructors module_1 and module_2 that both call the Delegate:

function Delegate(main, location) {
    this.module = null;
    this.init = function() { // you should do initialisation stuff directly in the
                             // constructor, not an `init` method
        this.module = new App[this.module_name](main, location, this.table);
        this.module.init();
    };
}
Delegate.prototype.test = function(){
    this.module.test();
};

function Module_1(main, location) {
    Delegate.call(this, main, location);
}
Module_1.prototype = Object.create(Delegate.prototype);
Module_1.prototype.table = 'debtor_group';
Module_1.prototype.module_name = 'module_group';


function Module_2(main, location) {
    Delegate.call(this, main, location);
}
Module_2.prototype = Object.create(Delegate.prototype);
Module_2.prototype.table = 'creditor_group';
Module_2.prototype.module_name = 'module_group';

answered Feb 20, 2015 at 12:07

Bergi

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1 Comment

clarkk Over a year ago

Your solutions is just what I was looking for.. But what does this line do? I can escape the line and the code still works Module_1.prototype = Object.create(Delegate.prototype);

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