blocks|key|342172|text|如果设置了global修饰符，则使用String的match()函数不会返回捕获的组，正如您发现的那样。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|342173|在这种情况下，您可能希望使用RegExp对象并调用其exec()函数。String的match()与RegExp的exec()函数global几乎完全相同，如果设置了global修饰符，普通的match()函数将不会返回捕获的组，而RegExp的exec()函数将返回。(注意here，还有其他地方)。|342174|另一个要记住的问题是，exec()不会返回大数组中的匹配项-它会一直返回匹配项，直到用完为止，在这种情况下，它会返回null。|342175|举个例子，你可以这样做：|342176|var+pattern+=+/t(e)(s)t/g;++//+Alternatively,+"new+RegExp('t(e)(s)t',+'g');"
var+match;++++

while+(match+=+pattern.exec(text))+{
++++//+Do+something+with+the+match+(["test",+"e",+"s"])+here...
}|code-block|syntax|javascript|342177|另一件要注意的事情是，RegExp.prototype.exec()和RegExp.prototype.test()对提供的字符串执行正则表达式，并返回第一个结果。每个顺序调用都将遍历结果集，并根据字符串中的当前位置更新RegExp.prototype.lastIndex。|342178|下面是一个示例:+//记住，示例和模式中有4个匹配项。lastIndex从0开始|342179|pattern.test(text);+//+pattern.lastIndex+=+4
pattern.test(text);+//+pattern.lastIndex+=+9
pattern.exec(text);+//+pattern.lastIndex+=+14
pattern.exec(text);+//+pattern.lastIndex+=+19

//+if+we+were+to+call+pattern.exec(text)+again+it+would+return+null+and+reset+the+pattern.lastIndex+to+0
while+(var+match+=+pattern.exec(text))+{
++++//+never+gets+run+because+we+already+traversed+the+string
++++console.log(match);
}

pattern.test(text);+//+pattern.lastIndex+=+4
pattern.test(text);+//+pattern.lastIndex+=+9

//+however+we+can+reset+the+lastIndex+and+it+will+give+us+the+ability+to+traverse+the+string+from+the+start+again+or+any+specific+position+in+the+string
pattern.lastIndex+=+0;

while+(var+match+=+pattern.exec(text))+{
++++//+outputs+all+matches
++++console.log(match);
}|342180|您可以找到有关如何使用RegExp+objects+on+the+MDN的信息(具体地说，这里是the+exec()+function的文档)。|342181|entityMap|0|LINK|mutability|MUTABLE|url|http://james.padolsey.com/javascript/regular-expressions-in-javascript-part-2/|1|https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp|2|https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp/exec^0|I|6|P|7|0|E|6|Q|6|Z|6|16|7|1E|6|1L|6|2O|7|38|6|3F|6|3U|4|0|0|B|6|1M|4|0|0|0|B|N|Z|N|32|Q|0|0|0|B|6|1G|6|Q|A|1|1C|J|2|0^^$0|@$1|2|3|4|5|6|7|1A|8|@$9|1B|A|1C|B|C]|$9|1D|A|1E|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|1F|8|@$9|1G|A|1H|B|C]|$9|1I|A|1J|B|C]|$9|1K|A|1L|B|C]|$9|1M|A|1N|B|C]|$9|1O|A|1P|B|C]|$9|1Q|A|1R|B|C]|$9|1S|A|1T|B|C]|$9|1U|A|1V|B|C]|$9|1W|A|1X|B|C]]|D|@$9|1Y|A|1Z|1|20]]|E|$]]|$1|H|3|I|5|6|7|21|8|@$9|22|A|23|B|C]|$9|24|A|25|B|C]]|D|@]|E|$]]|$1|J|3|K|5|6|7|26|8|@]|D|@]|E|$]]|$1|L|3|M|5|N|7|27|8|@]|D|@]|E|$O|P]]|$1|Q|3|R|5|6|7|28|8|@$9|29|A|2A|B|C]|$9|2B|A|2C|B|C]|$9|2D|A|2E|B|C]]|D|@]|E|$]]|$1|S|3|T|5|6|7|2F|8|@]|D|@]|E|$]]|$1|U|3|V|5|N|7|2G|8|@]|D|@]|E|$O|P]]|$1|W|3|X|5|6|7|2H|8|@$9|2I|A|2J|B|C]|$9|2K|A|2L|B|C]]|D|@$9|2M|A|2N|1|2O]|$9|2P|A|2Q|1|2R]]|E|$]]|$1|Y|3|-4|5|6|7|2S|8|@]|D|@]|E|$]]]|Z|$10|$5|11|12|13|E|$14|15]]|16|$5|11|12|13|E|$14|17]]|18|$5|11|12|13|E|$14|19]]]]

Using <code>String</code>'s <code>match()</code> function won't return captured groups if the global modifier is set, as you found out.

In this case, you would want to use a <code>RegExp</code> object and call its <code>exec()</code> function. <code>String</code>'s <code>match()</code> is almost identical to <code>RegExp</code>'s <code>exec()</code> function…except in cases like these. If the global modifier is set, the normal <code>match()</code> function won't return captured groups, while <code>RegExp</code>'s <code>exec()</code> function will. (Noted <a href="http://james.padolsey.com/javascript/regular-expressions-in-javascript-part-2/" rel="noreferrer">here</a>, among other places.)

Another catch to remember is that <code>exec()</code> doesn't return the matches in one big array—it keeps returning matches until it runs out, in which case it returns <code>null</code>.

So, for example, you could do something like this:

<pre><code>var pattern = /t(e)(s)t/g; // Alternatively, "new RegExp('t(e)(s)t', 'g');"
var match; 

while (match = pattern.exec(text)) {
 // Do something with the match (["test", "e", "s"]) here...
}
</code></pre>

Another thing to note is that <code>RegExp.prototype.exec()</code> and <code>RegExp.prototype.test()</code> execute the regular expression on the provided string and return the first result. Every sequential call will step through the result set updating <code>RegExp.prototype.lastIndex</code> based on the current position in the string.

Here's an example:
 // remember there are 4 matches in the example and pattern. lastIndex starts at 0

<pre><code>pattern.test(text); // pattern.lastIndex = 4
pattern.test(text); // pattern.lastIndex = 9
pattern.exec(text); // pattern.lastIndex = 14
pattern.exec(text); // pattern.lastIndex = 19

// if we were to call pattern.exec(text) again it would return null and reset the pattern.lastIndex to 0
while (var match = pattern.exec(text)) {
 // never gets run because we already traversed the string
 console.log(match);
}

pattern.test(text); // pattern.lastIndex = 4
pattern.test(text); // pattern.lastIndex = 9

// however we can reset the lastIndex and it will give us the ability to traverse the string from the start again or any specific position in the string
pattern.lastIndex = 0;

while (var match = pattern.exec(text)) {
 // outputs all matches
 console.log(match);
}
</code></pre>

You can find information on how to use <code>RegExp</code> objects <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp" rel="noreferrer">on the MDN</a> (specifically, here's the documentation for <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp/exec" rel="noreferrer">the <code>exec()</code> function</a>).

blocks|key|3326885|text|令我惊讶的是，我是第一个用我10年前寻找的答案回答这个问题的人(答案当时还不存在)。我也希望实际的规范作者会在我之前回答这个问题;)。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3326886|.matchAll已经添加到一些浏览器中。|offset|length|style|BOLD|3326887|在现代的javascript中，我们现在可以通过执行以下操作来实现这一点。|3326888|let+result+=+[...text.matchAll(/t(e)(s)t/g)];|code-block|syntax|javascript|3326889|3326890|3326891|我现在维护了一个同构的javascript库，它可以帮助进行很多这种类型的字符串解析。你可以在这里查看：string-saw。它有助于在使用命名捕获组时使.matchAll更易于使用。|3326892|一个例子就是|3326893|saw(text).matchAll(/t(e)(s)t/g)|3326894|它输出一个更加用户友好的匹配数组，如果你想获得更好的效果，你可以抛出命名的捕获组并获得一个对象数组。|3326895|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/icodeforlove/string-saw^0|0|0|9|0|0|0|0|0|1G|A|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|16|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|17|8|@$D|18|E|19|F|G]]|9|@]|A|$]]|$1|H|3|I|5|6|7|1A|8|@]|9|@]|A|$]]|$1|J|3|K|5|L|7|1B|8|@]|9|@]|A|$M|N]]|$1|O|3|-4|5|6|7|1C|8|@]|9|@]|A|$]]|$1|P|3|-4|5|6|7|1D|8|@]|9|@]|A|$]]|$1|Q|3|R|5|6|7|1E|8|@]|9|@$D|1F|E|1G|1|1H]]|A|$]]|$1|S|3|T|5|6|7|1I|8|@]|9|@]|A|$]]|$1|U|3|V|5|L|7|1J|8|@]|9|@]|A|$M|N]]|$1|W|3|X|5|6|7|1K|8|@]|9|@]|A|$]]|$1|Y|3|-4|5|6|7|1L|8|@]|9|@]|A|$]]]|Z|$10|$5|11|12|13|A|$14|15]]]]

I am surprised to see that I am the first person to answer this question with the answer I was looking for 10 years ago (the answer did not exist yet). I also was hoping that the actual spec writers would have answered it before me ;).

.matchAll has already been added to a few browsers.

In modern javascript we can now accomplish this by just doing the following.

<pre><code>let result = [...text.matchAll(/t(e)(s)t/g)];
</code></pre>

<a href="https://tc39.github.io/ecma262/#sec-string.prototype.matchall" rel="noreferrer">.matchAll spec</a>

<a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/matchAll" rel="noreferrer">.matchAll docs</a>

I now maintain an isomorphic javascript library that helps with a lot of this type of string parsing. You can check it out here: <a href="https://github.com/icodeforlove/string-saw" rel="noreferrer">string-saw</a>. It assists in making .matchAll easier to use when using named capture groups.

An example would be

<pre><code>saw(text).matchAll(/t(e)(s)t/g)
</code></pre>

Which outputs a more user-friendly array of matches, and if you want to get fancy you can throw in named capture groups and get an array of objects.

Why do Javascript sub-matches stop working when the <code>g</code> modifier is set?

<pre><code>var text = 'test test test test';

var result = text.match(/t(e)(s)t/);
// Result: ["test", "e", "s"]
</code></pre>

The above works fine, <code>result[1]</code> is <code>"e"</code> and <code>result[2]</code> is <code>"s"</code>.

<pre><code>var result = text.match(/t(e)(s)t/g);
// Result: ["test", "test", "test", "test"]
</code></pre>

The above ignores my capturing groups. Is the following the only valid solution?

<pre><code>var result = text.match(/test/g);
for (var i in result) {
 console.log(result[i].match(/t(e)(s)t/));
}
/* Result:
["test", "e", "s"]
["test", "e", "s"]
["test", "e", "s"]
["test", "e", "s"]
*/
</code></pre>

EDIT:

I am back again to happily tell you that 10 years later you can now do this (.matchAll has been added to the spec)

<pre><code>let result = [...text.matchAll(/t(e)(s)t/g)];
</code></pre>

JavaScript regular expressions and sub-matches

为什么在设置g修饰符时Javascript子匹配停止工作？var text = 'test test test test';var result = text.match(/t(e)(s)t/);// Result: ["test", "e", "s"]上面的代码运行良好，result[1]是"e"，result[2]...

问JavaScript正则表达式和子匹配
EN

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问JavaScript正则表达式和子匹配EN

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问JavaScript正则表达式和子匹配
EN