Edit in JSFiddle

//http://www.jermywells.com
//js abstraction

var SomeObject = function(){
    var self = this;
    var collection = new Array();
    var setHTML = function(sel, v){
        return document.getElementById(sel).innerHTML = v;
    };
    this.bindAddButton = function(){
        document.getElementById('add').onclick= function(){
            self.add();
        };
        self.setJsonOntoCollectionElem();
    };
    
    this.add = function(text){
        var e = document.getElementById('objToAdd');
        collection.push(text||e.value);
        e.value = '';
        self.setJsonOntoCollectionElem();
    };
    
    this.setJsonOntoCollectionElem = function(){
        setHTML('collection', JSON.stringify(collection));
    }
}

var someObj = new SomeObject();
someObj.bindAddButton();

TODO LIST: (enter text and click button)<br />
<input type="text" id="objToAdd" value="" />
<input type="button" id="add" value="add text" />
<br />
<div id="collection"></div>