这个javascript代码可以优化吗？

Question

如果当前页面URL在查询字符串中有一个参数'myid1'或'myid2'，对于我的网页中每个具有'rewrite'类的链接，我希望链接href的查询字符串被当前页面URL的查询字符串替换。我正在使用下面给出的代码。由于我是javascript的新手，我不确定它是否已经过优化。我希望它尽快执行。请帮忙。在此先感谢：）

<script type='text/javascript' src='https://ajax.googleapis.com/ajax/libs/jquery/1.6.4/jquery.min.js'></script>

<script type="text/javascript">
$(function() {
    var requestid = gup('myid1');
    if (requestid) {
        $("a.rewrite").each(function() {
            var base = this.href;
            var pos = base.indexOf("?");
            if (pos != -1) {
                base = base.substr(0, pos);
            }
            this.href = base + "?myid1=" + requestid;
        })
    }
    var requestid2 = gup('myid2');
    if (requestid2) {
        $("a.rewrite").each(function() {
            var base = this.href;
            var pos = base.indexOf("?");
            if (pos != -1) {
                base = base.substr(0, pos);
            }
            this.href = base + "?myid2=" + requestid2;
        })
    }
})

function gup( name )
{
  name = name.replace(/[\[]/,"\\\[").replace(/[\]]/,"\\\]");
  var regexS = "[\\?&]"+name+"=([^&#]*)";
  var regex = new RegExp( regexS );
  var results = regex.exec( window.location.href );
  if( results == null )
    return "";
  else
    return results[1];
}
</script>

<a href="http://www.website.com/?someid=1234" class="rewrite">Hyperlink</a>

Answer 1

$(function() {
    var requestid = gup('myid1');
    var requestid2 = gup('myid2');

    if (requestid || requestid2) {
        $("a.rewrite").each(function() {
            var base = this.href;
            var pos = base.indexOf("?");
            if (pos != -1) {
                base = base.substr(0, pos);
            }

            if (requestid){
                this.href = base + "?myid1=" + requestid;
                if (requesid2){
                    this.href += "?myid2=" + requestid;
                }
            } else {
                this.href = base + "?myid2=" + requestid;
            }

        })
    }

});

Answer 2

您提供的代码在两个方面效率低下：

1. 不必要的循环。它每次循环a.rewrite锚点以进行一次查询字符串匹配。它可以优化为一个循环;

正常表达式匹配

2. 重复计算。每个regexS函数都会执行gup，并且可以将其缩减为一个计算。

解决方案是：

1. 将window.location.href数据提取到一个可以在以后引用的变量中;

2. 将两个（或多个）循环合二为一，并在一个循环中完成所有替换。

这里优化的代码是：

//First you fetch the query string as key-value pairs in the window.location.href, this equals your gup function.

//This code, fetch the ?key1=value1&key2=value2 pair into an javaScript Object {'key1': 'value1', 'key2':'value2'}
var queryString = {}; 
var queryStringPattern = new RegExp("([^?=&]+)(=([^&]*))?", "g");
window.location.href.replace(
    queryStringPattern,
    function($0, $1, $2, $3) { queryString[$1] = $3; }
);

//Second you collect all the anchor with class rewrite and execute the replacement.

$("a.rewrite").each(function () {
  this.href.replace(
    queryStringPattern,
    function ($0, $1, $2, $3) {
      return queryString[$1] ? $1 +  "=" + queryString[$1] : $1 + '=' + $3;
    }
  )
});