qq_yEs先生_53252576
<script> function find(str,cha,num){ var x=str.indexOf(cha); for(var i=0;i<num;i++){ x=str.indexOf(cha,x+1); } return x; } var str="<!--1231-->",index,sub2; index = find(str,'-',2); sub2 = str.substring(4,index) document.write(sub2) </script>