替换变量[Javascript]时出现问题

我正在尝试修改谷歌代码Javascript文件，以便获得访问链接的经验。我是javascript的新手，我真的不知道如何表达我想要做的事情。我认为它应该看起来像这样：

var exp = 0 //Current exp
var level = 1; // User Level
var tolvl = level * 100 //Exp to 'level up'
function expchange (exp) {
  if (urlToCount <= 1) { //if they have visited the link once today
    exp+=10; //Change variable 'exp' to "variable"+10
  }
  else {
    exp+=5; // If more, change to "variable"+5
  }
  if (exp == tolvl ) { //If Variable 'exp' is equal to Variable 'tolvl'
    level+=1; //Change variable 'level' to 'variable'+1
}
//I need some kind of function to write Variables to HTML

我可能做错了什么，很抱歉脚本写得不好。感谢您的帮助

完整的参考代码：

// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Event listner for clicks on links in a browser action popup.
// Open the link in a new tab of the current window.
function onAnchorClick(event) {
  chrome.tabs.create({
    selected: true,
    url: event.srcElement.href
  });
  return false;
}
// Given an array of URLs, build a DOM list of those URLs in the
// browser action popup.
function buildPopupDom(divName, data) {
  var popupDiv = document.getElementById(divName);
  var ul = document.createElement('ul');
  popupDiv.appendChild(ul);
  for (var i = 0, ie = data.length; i < ie; ++i) {
    var a = document.createElement('a');
    a.href = data[i];
    a.appendChild(document.createTextNode(data[i]));
    a.addEventListener('click', onAnchorClick);
    var li = document.createElement('li');
    li.appendChild(a);
    ul.appendChild(li);
  }
}
// Search history to find up to ten links that a user has typed in,
// and show those links in a popup.
function buildTypedUrlList(divName) {
  // To look for history items visited in the last week,
  // subtract a week of microseconds from the current time.
  var microsecondsPerDay = 1000 * 60 * 60 * 24 ;
  var onedayAgo = (new Date).getTime() - microsecondsPerDay;
  // Track the number of callbacks from chrome.history.getVisits()
  // that we expect to get.  When it reaches zero, we have all results.
  var numRequestsOutstanding = 0;
  chrome.history.search({
      'text': '',              // Return every history item....
      'startTime': oneDayAgo  // that was accessed less than one week ago.
    },
    function(historyItems) {
      // For each history item, get details on all visits.
      for (var i = 0; i < historyItems.length; ++i) {
        var url = historyItems[i].url;
        var processVisitsWithUrl = function(url) {
          // We need the url of the visited item to process the visit.
          // Use a closure to bind the  url into the callback's args.
          return function(visitItems) {
            processVisits(url, visitItems);
          };
        };
        chrome.history.getVisits({url: url}, processVisitsWithUrl(url));
        numRequestsOutstanding++;
      }
      if (!numRequestsOutstanding) {
        onAllVisitsProcessed();
      }
    });

  // Maps URLs to a count of the number of times the user typed that URL into
  // the omnibox.
  var urlToCount = {};
  // Callback for chrome.history.getVisits().  Counts the number of
  // times a user visited a URL by typing the address.
  var processVisits = function(url, visitItems) {
    for (var i = 0, ie = visitItems.length; i < ie; ++i) {
      // Ignore items unless the user typed the URL.
      if (visitItems[i].transition != 'link') {
        continue;
      }
      if (!urlToCount[url]) {
        urlToCount[url] = 0;
      }
      urlToCount[url]++;
    }
    // If this is the final outstanding call to processVisits(),
    // then we have the final results.  Use them to build the list
    // of URLs to show in the popup.
    if (!--numRequestsOutstanding) {
      onAllVisitsProcessed();
    }
  };
  // This function is called when we have the final list of URls to display.
  var onAllVisitsProcessed = function() {
    // Get the top scorring urls.
    urlArray = [];
    for (var url in urlToCount) {
      urlArray.push(url);
    }
    // Sort the URLs by the number of times the user typed them.
    urlArray.sort(function(a, b) {
      return urlToCount[b] - urlToCount[a];
    });
    buildPopupDom(divName, urlArray.slice(0, 10));
  };
}
document.addEventListener('DOMContentLoaded', function () {
  buildTypedUrlList("typedUrl_div");
});
var exp = 0 //Current exp
var level = 1; // User Level
var tolvl = level * 100 //Exp to 'level up'
function expchange (exp) {
  if (urlToCount <= 1) { //if they have visited the link once today
    exp+=10; //Change variable 'exp' to "variable"+10
  }
  else {
    exp+=5; // If more, change to "variable"+5
  }
  if (exp == tolvl ) { //If Variable 'exp' is equal to Variable 'tolvl'
    level+=1; //Change variable 'level' to 'variable'+1
}
//I need some kind of function to write Variables to HTML