function setUri(para, val) {
      var strNewUrl = new String();
      var strUrl = new String();
      var url = window.location.href;
      strUrl = window.location.href;

      if (strUrl.indexOf("") != -1) {
        strUrl = strUrl.substr(strUrl.indexOf("") + 1);  //获取参数

        if (strUrl.toLowerCase().indexOf(para.toLowerCase()) == -1) { //如果没有找到参数,则直接赋值
          strNewUrl = url + "&" + para + "=" + val;
          window.location.href = strNewUrl;
        } else {
          var aParam = strUrl.split("&");

          for (var i = 0; i < aParam.length; i++) {
            if (aParam[i].substr(0, aParam[i].indexOf("=")).toLowerCase() == para.toLowerCase()) {
              aParam[i] = aParam[i].substr(0, aParam[i].indexOf("=")) + "=" + val;
            }
          }
          strNewUrl = url.substr(0, url.indexOf("") + 1) + aParam.join("&");
          window.location.href = strNewUrl;
        }
      } else {
        strUrl += "" + para + "=" + val;
        window.location.href = strUrl;
      }
    }

  //使用正则
    function setPara(para, val) {
      var newpar = "";
      var url = window.location.href;
      var pars = location.search.substring(1);

      var reg = new RegExp("(^|)" + para + "=([^&]*)(|$)");
      if (reg.test(pars)) {  //有需要的参数para

        var p1 = pars.split(para)[0];  //productID=100857&count=1&
        var p2 = pars.split(para)[1];  //=75825&coupval=1.5&addressID=358&invoiceID=1245&invoiceName=jesse

        if (p2.indexOf("&") > -1) {
          var p3 = p2.split("&")[0];
          if (p3 == "=" + val + "") {
            return false;
          }
          newpar = p1 + para + '=' + val + '&' + (p2.split(p3))[1];
        } else {
          if (p1) {
            newpar = p1 + para + '=' + val;
          } else {
            newpar = para + '=' + val;
          }
        }
      } else {
        if (url.indexOf("") == -1) {
          newpar = pars +"&"+ para + "=" + val;
        } else {
          newpar = pars + "&" + para + "=" + val;
        }
      }
      window.location.href = location.href.split('"" + newpar;
    }

<script>
window.onload = function () {
      var btn = document.getElementById("btnClick");

      btn.onclick = function () {

　　　　　　　　　　// url地址:http://localhost:54714/testuri.aspx"coupresId", 0);
　　　　　　　　　　setPara("coupresId", 0); 
　　　　} 
　　}
</script>

<input type="button" id="btnClick" value="重定义参数" />