Javascript 如何删除正则表达式开头和结尾的空白？

我为我的标记语言创建了一个javascript解析器。 我希望标签和内容之间没有空格，如下所示：

__underline a sentence __and more. 
(or correctly : __underline a sentence__ and more.)

致：

但第一种情况的结果是：

<u>underline a sentence </u>and more.

我的代码：

var tabML = ['\'','*','_'],
    tabHTML = ['em','strong','u']
    tag, char;
for(var i=0; i<tabML.length; i++){
    tag = tabHTML[i]; char = tabML[i];
    regex = new RegExp(char+char+'(.+)'+char+char, 'ig');
    txt = txt.replace(regex, '<'+tag+'>$1</'+tag+'>');
}

---

谢谢。

使用下面的正则表达式，然后用$1替换匹配的字符

试试这个。换成1美元。见演示

---

谢谢只需在两个下划线后添加\s*：\uuus*？\s*\uus\*

var tabML = ['\'','*','_'],
    tabHTML = ['em','strong','u']
    tag, char;
for(var i=0; i<tabML.length; i++){
    tag = tabHTML[i]; char = tabML[i];
    regex = new RegExp(char+char+'(.+)'+char+char, 'ig');
    txt = txt.replace(regex, '<'+tag+'>$1</'+tag+'>');
}

__\s*(.*?)\s*__\s*

> var s1 = "__underline a sentence __and more."
undefined
> var s2 = "__underline a sentence__ and more."
undefined
> s1.replace(/__\s*(.*?)\s*__\s*/g, '<u>$1</u> ')
'<u>underline a sentence</u> and more.'
> s2.replace(/__\s*(.*?)\s*__\s*/g, '<u>$1</u> ')
'<u>underline a sentence</u> and more.'

__(.*?)[ ]*__[ ]*

var re = /__(.*?)[ ]*__[ ]*/gm;
var str = '__underline a sentence __and more.\n__underline a sentence__ and more.';
var subst = '<u>$1</u> ';

var result = str.replace(re, subst);