Safely Attach Event Listeners in Javascript

Code Snippet to add an handler to an event listener

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function commonjsAddEvent( obj, type, fn ) {     if (obj.addEventListener) {         obj.addEventListener( type, fn, false );     }     else if (obj.attachEvent) {         obj["e"+type+fn] = fn;         obj[type+fn] = function()         {             obj["e"+type+fn]( window.event );         }         obj.attachEvent( "on"+type, obj[type+fn] );     }     else {         obj["on"+type] = obj["e"+type+fn];     } }

function commonjsAddEvent( obj, type, fn ) {
    if (obj.addEventListener) {
        obj.addEventListener( type, fn, false );
    }
    else if (obj.attachEvent) {
        obj["e"+type+fn] = fn;
        obj[type+fn] = function() 
        { 
            obj["e"+type+fn]( window.event ); 
        }
        obj.attachEvent( "on"+type, obj[type+fn] );
    }
    else {
        obj["on"+type] = obj["e"+type+fn];
    }
}

And below Code Snippet to remove the handler from the event listener

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01 02 03 04 05 06 07 08 09 10 11 12	function commonjsRemoveEvent( obj, type, fn ){     if(obj.removeEventListener){         obj.removeEventListener( type, fn, false );     }     else if(obj.detachEvent){         obj.detachEvent("on"+type, obj[type+fn]);         obj[type+fn]=null;         obj["e"+type+fn]=null;     }     else         obj["on"+type] = null; }

function commonjsRemoveEvent( obj, type, fn ){
    if(obj.removeEventListener){
        obj.removeEventListener( type, fn, false );
    }
    else if(obj.detachEvent){
        obj.detachEvent("on"+type, obj[type+fn]);
        obj[type+fn]=null;
        obj["e"+type+fn]=null;
    }
    else
        obj["on"+type] = null;
}