How to apply a function to multiple objects? (Pure Javascript)

Question

For example, I have a div within a variable obj

 obj = document.getElementById("objeto");

..I want a function to be applied to it that way

 window.onload = function(){
    window.onclick = function (){
       obj = document.getElemntById("obj");
       obj.ver();
    }
    function ver(){
       this.style.backgroundColor = "#333333";
    }
 }  

How could I make this application work?

My complete code, abixo:

    <script>        
    HTMLElement.prototype.mover = function(){

        movendo = false;
        valor = 0;
        calc = 0;
        resto = 0;
        this.onmousedown = function(e){                
            movendo = true;
            valor = e.pageX + document.body.scrollLeft;     
            calc = valor - this.offsetLeft;
            resto = this.offsetWidth - calc;

            valor2 = e.pageY + document.body.scrollTop;     
            calc2 = valor2 - this.offsetTop;
            resto2 = this.offsetHeight - calc2;

            this.style.cursor = "move";

        };            
        window.onmouseup = function(){

            movendo = false;
            this.style.cursor = "pointer";        
        };

       window.onmousemove = function(e){
            if( movendo == true ) {

                this.style.left = (e.pageX + document.body.scrollLeft) - this.offsetWidth + resto + "px";
                this.style.top = (e.pageY + document.body.scrollTop) - this.offsetHeight + resto2 + "px";

            }
        };
    }

    window.onload = function(){            
        obj = document.getElementById("obj");
        obj.mover();            
    }         
    </script>

Answer 1

To do this you have to extend the prototype and add this method to the elements.

Example: http://jsfiddle.net/xYfMa/

HTMLElement.prototype.ver = function() {
    this.style.backgroundColor = "#333333";
}

window.onload = function () {
    window.onclick = function () {
        obj = document.getElementById("obj");
        obj.ver();
    }
}

Using the word prototype access to the prototype of all elements and this method is available in all elements. Just be careful not to write over existing methods, because this tool is very powerful.