添加 JavaScript 变量以单击以调用链接

我正在尝试做的是添加一个javascript变量到单击以调用href，以便每当电话号码从javascript更改时，单击呼叫href也会更改。定义变量的 javascript 具有默认值（例如：1-800-555-1212），但只要页面加载，tfid 定义不同的电话号码（例如：http：//www.domain.com？tfid=8663337777），就可以更改。

以下是当前内容的示例：

<a href="tel:<this phone number needs to be dynamic as well>">Call this number: <script language="javascript" >
  key = getVar("keyword");
  tn = getVar("tfid");
  source = getVar("source");
  content = getVar("content");
  campaign = getVar("campaign");
  if(tn!="")
  {
  setcookie(key,tn);
  }
  getcookie(); 
  </script></a>

编辑：

显示或切换的所有元素，我在下面包含了每当页面加载时调用的 javascript：

// JavaScript Document start
//function to set cookie from the URL
function pixelfire(debug)
{
var phone_number=getVar("phone_number");
var keyword=getVar("keyword");
var source=getVar("source");
if(keyword)
{
    //document.write("set phone number "+phone_number);
    //document.write("set keyword "+keyword);
    setcookie(keyword,phone_number);
    //document.write("back from set cookie");
}
else
{
    var keyword=get_named_cookie("MM_Keyword");
    var phone_number=get_named_cookie("MM_TrackableNumber");
    //document.write("retrieved keyword "+keyword);
    //document.write("retrieved phone number "+phone_number);
    if(keyword)
    {
    }
    else
    {
        return null;
    }
}
if(debug)
{
document.write("here are cookies<BR><P>"+document.cookie);
}
var campaign=getVar("campaign");
var content=getVar("content");
//document.write("location is "+location);
var url="http://www.mongoosemetrics.com/pixelfire.php?phone_number="+phone_number;
var url = url + "&keyword="+keyword;
var url = url + "&source="+source;
var url = url + "&campaign="+campaign;
var url = url + "&content="+content;
//document.write("url is "+ url);
myImage= new Image();
myImage.src=url;
}
function setcookie(key,tn,path){
        index = -1;
        var today = new Date();
        today.setTime( today.getTime() );
        var cookie_expire_date = new Date(today.getTime() + (365* 86400000)); 
        document.cookie="MM_TrackableNumber="+tn+";path=/;expires="+cookie_expire_date.toGMTString();
        document.cookie="MM_Keyword="+key+";path=/;expires="+cookie_expire_date.toGMTString();
}
//function to retrive the cookie
function getcookie(){
    //plcae your default phone number to show in case cookie is not set
    defaultphone="8005551212";
    if(document.cookie){ //check if there is a cookie set 
          index = document.cookie.indexOf("MM_TrackableNumber");
          if (index != -1){
                namestart = (document.cookie.indexOf("=", index) + 1);
                nameend = document.cookie.indexOf(";", index);
                if (nameend == -1) {nameend = document.cookie.length;}
                document.write(formatnumber(document.cookie.substring(namestart, nameend)));
          }
            else
            {
            document.write(formatnumber(defaultphone));
            }
    }
    else
    {
    document.write(formatnumber(defaultphone));
    }
}
function get_named_cookie(name)
{
    if(document.cookie)
    {
        index=document.cookie.indexOf(name);
        if (index != -1)
        {
            namestart = (document.cookie.indexOf("=", index) + 1);
                        nameend = document.cookie.indexOf(";", index);
                        if (nameend == -1) {nameend = document.cookie.length;}
            var ret_one = document.cookie.substring(namestart, nameend);
            return ret_one; 
        }
    }
}
//function to format the phonenumber to (123) 456-7890
function formatnumber(num)
{
    _return="1-";
    var ini = num.substring(0,3);
    _return+=ini+"-";
    var st = num.substring(3,6);
    _return+=st+"-";
    var end = num.substring(6,10);
    _return+=end;
    return _return;
}
function getVar(name)
         {
         get_string = document.location.search;         
         return_value = '';
         do { //This loop is made to catch all instances of any get variable.
            name_index = get_string.indexOf(name + '=');
            if(name_index != -1)
              {
              get_string = get_string.substr(name_index + name.length + 1, get_string.length - name_index);
              end_of_value = get_string.indexOf('&');
              if(end_of_value != -1)                
                value = get_string.substr(0, end_of_value);                
              else                
                value = get_string;                
              if(return_value == '' || value == '')
                 return_value += value;
              else
                 return_value += ', ' + value;
              }
            } while(name_index != -1)
         //Restores all the blank spaces.
         space = return_value.indexOf('+');
         while(space != -1)
              { 
              return_value = return_value.substr(0, space) + ' ' + 
              return_value.substr(space + 1, return_value.length);
              space = return_value.indexOf('+');
              }
         return(return_value);        
         }
/*end*/

尽管这听起来很简单（我知道它不是），但我需要<a>标签来执行此操作：<a href="tel:FILL THIS WITH EITHER THE DEFAULT NUMBER OR THE NEW NUMBER DEFINED BY THE TFID URL">