js 设置断点技术

function inspect(inspector,title){  var expression,result;  if('ignore' in arguments.callee) return ;  while(true){    var message='';if(title) message=title+'\n';if(expression) message+='\n'+expression+'==>'+result+'\n';else expression='';message+='enter an expression to evaluate';expression=prompt(message,expression);if(!expression) return;result=inspector(expression);  }}function factorial(n){ var inspector=function($){return eval($);} inspect(inspector,'enterion factorial()'); var result=1; while(n>1){  result=result * n;;  n--;  inspect(inspector,'factorial() loop'); } inspect(inspector,'exiting factorial()'); return result;}