Question

36

Javascript: better way to add dynamic methods?

rated 0 times [ 43] [ 7] / answers: 1 / hits: 32708 / 15 Years ago, wed, february 25, 2009, 12:00:00

I'm wondering if there's a better way to add dynamic methods to an existing object. Basically, I am trying to assemble new methods dynamically and then append them to an existing function.

This demo code works.

builder = function(fn, methods){



    //method builder

    for(p in methods){

        method = 'fn.' + p + '=' + methods[p];

        eval(method);

    }



    return fn;

}

test = {}

test = builder(test, {'one':'function(){ alert(one); }','two':'function(){ alert(two); }'} );



test.one();

test.two();

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chyanne

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answered 15 Years ago yesseniadajab · Accepted Answer

You don't need to eval them each time.

You can create existing function objects, then assign them as properties to your objects.

var methods = {

  'increment': function() { this.value++; },

  'display' : function() { alert(this.value); }

};



function addMethods(object, methods) {

  for (var name in methods) {

    object[name] = methods[name];

  }

};



var obj = { value: 3 };

addMethods(obj, methods);

obj.display();  // 3

obj.increment();

obj.display();  // 4

The canonical, object-oriented way however, is to use constructors and prototypes, but this isn't really dynamic in that each object you construct will have the same methods:

function MyObj(value) {

  this.value = value;

};

MyObj.prototype.increment = function() {

  this.value++;

};

MyObj.prototype.display = function() {

  alert(this.value);

}

var obj = new MyObj(3);

obj.display();  // 3

obj.increment();

obj.display();  // 4