js操作checkbox的disabled

function DefaultClick(cbAvailable,cbDefault)
    {
        var left=document.getElementById(cbAvailable);
        var right=document.getElementById(cbDefault);
        var selectState=left.checked;
        //right.disabled=true;
        if(right.checked==true)
        {          
            //left.checked!=selectState;
            left.checked=true;          
        }
        else
        {  
            //left.checked!=selectState;
            //right.parentNode.disabled=false;
            //right.disabled=false;
            //right.style.display="none";      
        }
    }