var bNames='button_home button_services button_contact'.split(' '); var path='images/', btn=new Array(); 
function Button(name){ this.on=new Image(); this.on.src=path+name+'_on.gif'; this.off=new Image(); this.off.src=path+name+'_off.gif'; } 
for(i=0; i<bNames.length; i++) btn[bNames[i]]=new Button(bNames[i]); 
function rollOn(name){ document[name].src=btn[name].on.src; } 
function rollOff(name) { document[name].src=btn[name].off.src; }