JavaScript 正则表达式捕获并替换可选部分

Question

我发现很难在 JavaScript 中使用 Regex 对以下行执行捕获和替换:

// Lines:
This is <span>foo</span>.
This is <span>(Capital) foo</span>.
This is <span>foo (Plural)</span>.
This is <span>(Capital) foo (Plural)</span>.

我需要This is foo.来实现上述所有内容。

我尝试过:

var pattern = /<span>(\(Capital\))?\s?(\w+)\s?(\(Plural\))?<\/span>/;

var text1 = "This is <span>foo</span>";
var text2 = "This is <span>(Capital) foo</span>";
var text3 = "This is <span>foo (Plural)</span>";
var text4 = "This is <span>(Capital) foo (Plural)</span>";

text1.replace(pattern, function(_, m){ return m; });
text2.replace(pattern, function(_, m){ return m; });
text3.replace(pattern, function(_, m){ return m; });
text4.replace(pattern, function(_, m){ return m; });

但它不起作用。

Answer 1

您可以使用下面的正则表达式，

<span>(?:\(Capital\))?\s*(\w+)\s*(?:\(Plural\))?<\/span>

将匹配的字符替换为组索引 1 中的字符。

DEMO

> "This is <span>foo</span>.".replace(/<span>(?:\(Capital\))?\s*(\w+)\s*(?:\(Plural\))?<\/span>/g, '$1');
'This is foo.'
> "This is <span>(Capital) foo</span>.".replace(/<span>(?:\(Capital\))?\s*(\w+)\s*(?:\(Plural\))?<\/span>/g, '$1');
'This is foo.'
> "This is <span>foo (Plural)</span>.".replace(/<span>(?:\(Capital\))?\s*(\w+)\s*(?:\(Plural\))?<\/span>/g, '$1');
'This is foo.'
> "This is <span>(Capital) foo (Plural)</span>.".replace(/<span>(?:\(Capital\))?\s*(\w+)\s*(?:\(Plural\))?<\/span>/g, '$1');
'This is foo.'