js获取指定字符前/后的字符串

<script type="text/javascript"> 
/* 
  string 字符串; 
  str 指定字符; 
  split(),用于把一个字符串分割成字符串数组; 
  split(str)[0],读取数组中索引为0的值（第一个值）,所有数组索引默认从0开始; 
 */
function getStr(string,str){ 
    var str_before = string.split(str)[0]; 
    var str_after = string.split(str)[1]; 
    alert("前："+str_before+" - 后："+str_after); 
} 
</script> 

例

var st = "javascript:zhifu("index.php?s=/addon/xxxx/Alipay/index/cartid/1964/addid/162/invid/648/couponsid/11/paytype/2/type/3/fu/38.8/giveid/70,/givenum/1,/voucher//default",162)";

var before_str = getStr(st,"giveid");
alert(before_str);

结果：

javascript:zhifu("index.php?s=/addon/xxxx/Alipay/index/cartid/1964/addid/162/invid/648/couponsid/11/paytype/2/type/3/fu/38.8/