首先，我只是为自己创建了一个正则表达式，该表达式将匹配项目中所有头文件列表中的所有唯一外部库路径。我一周前问过一个关于制作该正则表达式的问题。
我开始四处看看，以了解异步和变成Web worker时的行为。为了方便和可靠，我创建了在所有三种模式下运行的通用文件：
/** 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，而不是将其粘贴到这里，而是将其上传到非常可靠的Web托管：Demo - Test data。
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着的差异。我得到的结果是：
- 火狐浏览器
[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，使用我的特定正则表达式，同步循环和异步循环之间的区别微不足道。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。这是对旧功能的更改：
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：
- 火狐浏览器
[WORKER]: Time elapsed:0.062s[WORKER-SYNC]: Time elapsed:0.023s[TIMEOUT]: Time elapsed:12.250s（请注意：每分钟都变得越来越奇怪）[LOOP]: Time elapsed:0.006s
谁能解释这种速度差异？