passing this (the object) into one of the objects methods nested methods
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Sorry for the long winded title, but I think it summaries my problem

I have created a jsfiddle to cut down and create a simplified problem of my dilemma
http://jsfiddle.net/afw6k/3/

    <input id="txtA"/>
    <!-- after setupOnclick is executed my onlick for txtA should be onclick="someObj.log("Clicked!")"-->
    <script>
        function someObject(field){
            this.field = field;
            
            this.log = function(msg){
                if(this.field.value != "") this.field.value += ", ";
                this.field.value += msg
            }
                    
            this.setupOnlick = function(){ 
                field.onlick = function(){//So how do I pass this (as in someObject) to this?
                    this.log("Clicked!"); //As if I have written someObj.log("Clicked!");
                }
            }
        }
        
        var someObj = new someObject(document.getElementById("txtA"));
        someObj.setupOnlick();
    </script>

I'm not trying to simply write something to a textbox when clicked, but the above is a simplified version of what I am trying to accomplish here.


Passing this (the object) into an objects functions nested function

Or is there a far better way to accomplish this?