WebWorker 计算缓慢的 regexp 匹配要慢得多(3x)-只有 firefox

首先，我自己创建了一个正则表达式，它将匹配项目中所有头文件列表中的所有唯一外部库路径。一周前。

我开始到处干预，看看它在异步和转变为 web worker 时会有什么反应。为了方便和可靠，我创建了这个通用文件，它可以在所有三种模式下运行:

/** Will call result() callback with every match it founds. Asynchronous unless called
*  with interval = -1.
*  Javadoc style comment for Arnold Rimmer and other Java programmers:
*
* @param regex regular expression to match in string
* @param string guess what
* @param result callback function that accepts one parameter, string match
* @param done callback on finish, has no parameters
* @param interval delay (not actual interval) between finding matches. If -1,
*        function  will be blocking
* @property working false if loop isn't running, otherwise contains timeout ID
*           for use with clearTimeout
* @property done copy of done parameter
* @throws heavy boulders
**/
function processRegex(regex, string, result, done, interval) {
var m;
//Please tell me interpreter optimizes this
interval = typeof interval!='number'?1:interval;
//And this
processRegex.done = done;
while ((m = regex.exec(string))) {
Array.prototype.splice.call(m,0,1);
var path = m.join("");
//It's good to keep in mind that result() slows down the process
result(path);
if (interval>=0) {
processRegex.working = setTimeout(processRegex,
interval, regex, string,
result, done, interval);
// Comment these out for maximum speed
processRegex.progress = regex.lastIndex/string.length;
console.log("Progress: "+Math.round(processRegex.progress*100)+"%");
return;
}
}


processRegex.working = false;
processRegex.done = null;
if (typeof done=="function")
done();
}
processRegex.working = false;

我创建了一个测试文件，而不是粘贴在这里，我上传了非常可靠的网络托管: 演示-测试数据。

令我感到非常惊讶的是，Web worker 和 RegExp 的浏览器执行之间存在如此显著的差异。我得到的结果是:

• Mozilla Firefox
  • [WORKER]: Time elapsed:16.860s
  • [WORKER-SYNC]: Time elapsed:16.739s
  • [TIMEOUT]: Time elapsed:5.186s
  • [LOOP]: Time elapsed:5.028s

您还可以看到，对于我的特定正则表达式，同步循环和异步循环之间的区别是微不足道的。我尝试使用匹配列表而不是前瞻表达式，结果发生了很大变化。以下是对旧函数的更改:

function processRegexUnique(regex, string, result, done, interval) {
var matchList = arguments[5]||[];
... same as before ...
while ((m = regex.exec(string))) {
... same as before ...
if (matchList.indexOf(path)==-1) {
result(path);
matchList.push(path);
}
if (interval>=0) {
processRegex.working = setTimeout(processRegex, interval,
regex, string, result,
done, interval, matchList);
... same as before ...
}
}
... same as before ...
}

结果是:

• Mozilla Firefox
  • [WORKER]: Time elapsed:0.062s
  • [WORKER-SYNC]: Time elapsed:0.023s
  • [TIMEOUT]: Time elapsed:12.250s(提醒自己: 它变得越来越怪异的每一分钟)
  • [LOOP]: Time elapsed:0.006s

有人能解释这种速度上的差异吗？