[devote]

var checkboxs = document.getElementsByTagName('input'),
    eventType = document.addEventListener ? ["addEventListener", ""] : ["attachEvent", "on"];

for( var i = 0; i < checkboxs.length; i++ ) {
    checkboxs[ i ][ eventType[ 0 ] ]( eventType[ 1 ] + "click", function( e ){
        e = e || window.event;
        handler.call( e.target || e.srcElemnt, e );
    }, false );
}

function handler( e ){
    document.getElementById('val').value = this.value;
}