首先,我刚刚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所有唯一的外部库路径。一周前我问了一个关于制作regexp的问题。
我开始摆弄它,看看它在异步和变成web worker时的行为。为了方便和可靠,我创建了这个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,而不是粘贴在这里,我把它上传到非常可靠的网络托管:Demo -测试数据。
我发现非常令人惊讶的是,在web worker和浏览器执行RegExp之间存在如此显著的差异。我得到的结果:
- 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。我试图使用一个匹配列表,而不是一个向前看的表达式,结果改变了很多。下面是对旧函数的修改:
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 ...
}
和结果:
- Mozilla Firefox
-
[WORKER]: Time elapsed:0.062s
-
[WORKER-SYNC]: Time elapsed:0.023s
-
[TIMEOUT]: Time elapsed:12.250s
(自我提醒:每分钟都变得越来越奇怪) -
[LOOP]: Time elapsed:0.006s
-
谁能解释这种速度上的差异?
经过一系列测试,我确认这是一个Mozilla Firefox问题(它影响了我尝试过的所有windows桌面版本)。对于Google Chrome, Opera,甚至Firefox移动版,regexp匹配都是相同的,无论是否工作。
如果您需要修复此问题,请务必在bugzilla上的bug报告中投票。