var str="ABC[000] ABC[000] ABC[000] ABC[000] ABC[000] ABC[000] ABC[000] ABC[000].";var reg=/(ABC\[)(\d{3})(\])/g;var index=-1;str = str.replace(reg, function(a,b,c,d){ return b+("000"+Math.floor((++index)*1/2)).substring(1,4)+d;});str