缩小：使用正则表达式从JavaScript代码中删除换行符

出于混淆的纯粹目的，前三行似乎很好地清除了脚本中不必要的输入

有人能告诉我1-4行的实际功能吗？从试错中我知道的唯一一件事是，如果我把第四行注释掉，网站就会工作，如果我把它留在原地，网站就会崩溃

<?php

header("Content-type: text/javascript; charset=UTF-8");   
ob_start("compress"); 
function compress($buffer) 
{
    # remove extra or unneccessary new line from javascript
    $buffer = preg_replace('/([;])\s+/', '$1', $buffer);
    $buffer = preg_replace('/([}])\s+(else)/', '$1else', $buffer);
    $buffer = preg_replace('/([}])\s+(var)/', '$1;var', $buffer);
    $buffer = preg_replace('/([{};])\s+(\$)/', '$1\$', $buffer);

    return $buffer;
}

所有四个正则表达式的剖析
让我们试着剖析每一个正则表达式

第一个正则表达式

$buffer = preg_replace('/([;])\s+/', '$1', $buffer);

$buffer = preg_replace('/([}])\s+(else)/', '$1else', $buffer);

$buffer = preg_replace('/([}])\s+(var)/', '$1;var', $buffer);

$buffer = preg_replace('/([{};])\s+(\$)/', '$1\$', $buffer);

解释

(      # beginning of the first capturing group
 [;]   # match the literal character ';'
)      # ending of the first capturing group
\s+    # one or more whitespace characters (including newlines)

(      # beginning of the first capturing group
 [}]   # match the literal character ';'
)      # ending of the first capturing group
\s+    # one or more whitespace characters
(else) # match and capture 'else'

(      # beginning of the first capturing group
 [}]   # match the literal character ';'
)      # ending of the first capturing group
\s+    # one or more whitespace characters
(var)  # match and capture 'var'

(      # beginning of the first capturing group
 [{};] # match the literal character '{' or '}' or ';'
)      # ending of the first capturing group
\s+    # one or more whitespace characters
(      # beginning of the second capturing group
 \$    # match the literal character '$'
)      # ending of the second capturing group

上面的正则表达式删除分号后面紧跟的任何空格
（[；]）
是一个捕获组，这意味着如果找到匹配项，它将存储到反向引用中，以便我们以后使用它。例如，如果我们的字符串是
foo
，则表达式将匹配
和空白字符。这里的替换模式是
$1
，这意味着整个匹配的字符串将被替换为一个分号


第二个正则表达式

$buffer = preg_replace('/([;])\s+/', '$1', $buffer);

$buffer = preg_replace('/([}])\s+(else)/', '$1else', $buffer);

$buffer = preg_replace('/([}])\s+(var)/', '$1;var', $buffer);

$buffer = preg_replace('/([{};])\s+(\$)/', '$1\$', $buffer);

解释

(      # beginning of the first capturing group
 [;]   # match the literal character ';'
)      # ending of the first capturing group
\s+    # one or more whitespace characters (including newlines)

(      # beginning of the first capturing group
 [}]   # match the literal character ';'
)      # ending of the first capturing group
\s+    # one or more whitespace characters
(else) # match and capture 'else'

(      # beginning of the first capturing group
 [}]   # match the literal character ';'
)      # ending of the first capturing group
\s+    # one or more whitespace characters
(var)  # match and capture 'var'

(      # beginning of the first capturing group
 [{};] # match the literal character '{' or '}' or ';'
)      # ending of the first capturing group
\s+    # one or more whitespace characters
(      # beginning of the second capturing group
 \$    # match the literal character '$'
)      # ending of the second capturing group

上面的正则表达式删除了右大括号（
}
）和
else
之间的任何空格。这里的替换模式是
$1else
，这意味着带空格的字符串将被第一个捕获组
（[}]）
（仅为分号）捕获的内容替换，然后是关键字
else
。没什么大不了的


第三个正则表达式

$buffer = preg_replace('/([;])\s+/', '$1', $buffer);

$buffer = preg_replace('/([}])\s+(else)/', '$1else', $buffer);

$buffer = preg_replace('/([}])\s+(var)/', '$1;var', $buffer);

$buffer = preg_replace('/([{};])\s+(\$)/', '$1\$', $buffer);

解释

(      # beginning of the first capturing group
 [;]   # match the literal character ';'
)      # ending of the first capturing group
\s+    # one or more whitespace characters (including newlines)

(      # beginning of the first capturing group
 [}]   # match the literal character ';'
)      # ending of the first capturing group
\s+    # one or more whitespace characters
(else) # match and capture 'else'

(      # beginning of the first capturing group
 [}]   # match the literal character ';'
)      # ending of the first capturing group
\s+    # one or more whitespace characters
(var)  # match and capture 'var'

(      # beginning of the first capturing group
 [{};] # match the literal character '{' or '}' or ';'
)      # ending of the first capturing group
\s+    # one or more whitespace characters
(      # beginning of the second capturing group
 \$    # match the literal character '$'
)      # ending of the second capturing group

这与以前的正则表达式相同。这里唯一的区别是关键字-
var
而不是
else
。分号字符在JavaScript中是可选的。但是，如果您想在一行中编写多个语句，解释器无法知道它们是多行语句，因此a
来终止每个语句


第四个正则表达式

$buffer = preg_replace('/([;])\s+/', '$1', $buffer);

$buffer = preg_replace('/([}])\s+(else)/', '$1else', $buffer);

$buffer = preg_replace('/([}])\s+(var)/', '$1;var', $buffer);

$buffer = preg_replace('/([{};])\s+(\$)/', '$1\$', $buffer);

解释

(      # beginning of the first capturing group
 [;]   # match the literal character ';'
)      # ending of the first capturing group
\s+    # one or more whitespace characters (including newlines)

(      # beginning of the first capturing group
 [}]   # match the literal character ';'
)      # ending of the first capturing group
\s+    # one or more whitespace characters
(else) # match and capture 'else'

(      # beginning of the first capturing group
 [}]   # match the literal character ';'
)      # ending of the first capturing group
\s+    # one or more whitespace characters
(var)  # match and capture 'var'

(      # beginning of the first capturing group
 [{};] # match the literal character '{' or '}' or ';'
)      # ending of the first capturing group
\s+    # one or more whitespace characters
(      # beginning of the second capturing group
 \$    # match the literal character '$'
)      # ending of the second capturing group

这里的替换模式是
$1\$
，这意味着整个匹配的字符串将被第一个捕获组
（[{}；]）
所匹配的字符串替换，然后是一个文本
$
字符

旁注
这个答案只是为了解释这四个正则表达式及其作用。表达式可以改进很多，但我不打算讨论，因为这不是正确的方法。正如Qtax在评论中指出的那样，您确实应该使用适当的JS minifier来完成此任务。你可能想去看看——它看起来很整洁

如果你仍然不知道它是如何工作的，不要担心。一开始学习正则表达式可能很困难。我建议你使用这个网站-。这是学习正则表达式的一个相当不错的资源。如果你在找一本书，你可能想看看Jeffrey Friedl写的。
对所有四个正则表达式的剖析
让我们试着剖析每一个正则表达式

第一个正则表达式

$buffer = preg_replace('/([;])\s+/', '$1', $buffer);

$buffer = preg_replace('/([}])\s+(else)/', '$1else', $buffer);

$buffer = preg_replace('/([}])\s+(var)/', '$1;var', $buffer);

$buffer = preg_replace('/([{};])\s+(\$)/', '$1\$', $buffer);

解释

(      # beginning of the first capturing group
 [;]   # match the literal character ';'
)      # ending of the first capturing group
\s+    # one or more whitespace characters (including newlines)

(      # beginning of the first capturing group
 [}]   # match the literal character ';'
)      # ending of the first capturing group
\s+    # one or more whitespace characters
(else) # match and capture 'else'

(      # beginning of the first capturing group
 [}]   # match the literal character ';'
)      # ending of the first capturing group
\s+    # one or more whitespace characters
(var)  # match and capture 'var'

(      # beginning of the first capturing group
 [{};] # match the literal character '{' or '}' or ';'
)      # ending of the first capturing group
\s+    # one or more whitespace characters
(      # beginning of the second capturing group
 \$    # match the literal character '$'
)      # ending of the second capturing group

上面的正则表达式删除分号后面紧跟的任何空格
（[；]）
是一个捕获组，这意味着如果找到匹配项，它将存储到反向引用中，以便我们以后使用它。例如，如果我们的字符串是
foo
，则表达式将匹配
和空白字符。这里的替换模式是
$1
，这意味着整个匹配的字符串将被替换为一个分号


第二个正则表达式

$buffer = preg_replace('/([;])\s+/', '$1', $buffer);

$buffer = preg_replace('/([}])\s+(else)/', '$1else', $buffer);

$buffer = preg_replace('/([}])\s+(var)/', '$1;var', $buffer);

$buffer = preg_replace('/([{};])\s+(\$)/', '$1\$', $buffer);

解释

(      # beginning of the first capturing group
 [;]   # match the literal character ';'
)      # ending of the first capturing group
\s+    # one or more whitespace characters (including newlines)

(      # beginning of the first capturing group
 [}]   # match the literal character ';'
)      # ending of the first capturing group
\s+    # one or more whitespace characters
(else) # match and capture 'else'

(      # beginning of the first capturing group
 [}]   # match the literal character ';'
)      # ending of the first capturing group
\s+    # one or more whitespace characters
(var)  # match and capture 'var'

(      # beginning of the first capturing group
 [{};] # match the literal character '{' or '}' or ';'
)      # ending of the first capturing group
\s+    # one or more whitespace characters
(      # beginning of the second capturing group
 \$    # match the literal character '$'
)      # ending of the second capturing group

上面的正则表达式删除了右大括号（
}
）和
else
之间的任何空格。这里的替换模式是
$1else
，这意味着带空格的字符串将被第一个捕获组
（[}]）
（仅为分号）捕获的内容替换，然后是关键字
else
。没什么大不了的


第三个正则表达式

$buffer = preg_replace('/([;])\s+/', '$1', $buffer);

$buffer = preg_replace('/([}])\s+(else)/', '$1else', $buffer);

$buffer = preg_replace('/([}])\s+(var)/', '$1;var', $buffer);

$buffer = preg_replace('/([{};])\s+(\$)/', '$1\$', $buffer);

解释

(      # beginning of the first capturing group
 [;]   # match the literal character ';'
)      # ending of the first capturing group
\s+    # one or more whitespace characters (including newlines)

(      # beginning of the first capturing group
 [}]   # match the literal character ';'
)      # ending of the first capturing group
\s+    # one or more whitespace characters
(else) # match and capture 'else'

(      # beginning of the first capturing group
 [}]   # match the literal character ';'
)      # ending of the first capturing group
\s+    # one or more whitespace characters
(var)  # match and capture 'var'

(      # beginning of the first capturing group
 [{};] # match the literal character '{' or '}' or ';'
)      # ending of the first capturing group
\s+    # one or more whitespace characters
(      # beginning of the second capturing group
 \$    # match the literal character '$'
)      # ending of the second capturing group

这与以前的正则表达式相同。这里唯一的区别是关键字-
var
而不是
else
。分号字符在JavaScript中是可选的。但是，如果您想在一行中编写多个语句，解释器无法知道它们是多行语句，因此a
来终止每个语句


第四个正则表达式

$buffer = preg_replace('/([;])\s+/', '$1', $buffer);

$buffer = preg_replace('/([}])\s+(else)/', '$1else', $buffer);

$buffer = preg_replace('/([}])\s+(var)/', '$1;var', $buffer);

$buffer = preg_replace('/([{};])\s+(\$)/', '$1\$', $buffer);

解释

(      # beginning of the first capturing group
 [;]   # match the literal character ';'
)      # ending of the first capturing group
\s+    # one or more whitespace characters (including newlines)

(      # beginning of the first capturing group
 [}]   # match the literal character ';'
)      # ending of the first capturing group
\s+    # one or more whitespace characters
(else) # match and capture 'else'

(      # beginning of the first capturing group
 [}]   # match the literal character ';'
)      # ending of the first capturing group
\s+    # one or more whitespace characters
(var)  # match and capture 'var'

(      # beginning of the first capturing group
 [{};] # match the literal character '{' or '}' or ';'
)      # ending of the first capturing group
\s+    # one or more whitespace characters
(      # beginning of the second capturing group
 \$    # match the literal character '$'
)      # ending of the second capturing group

这里的替换模式是
$1\$
，这意味着整个匹配的字符串将被第一个捕获组
（[{}；]）
所匹配的字符串替换，然后是一个文本
$
字符

旁注
这个答案只是为了解释这四个正则表达式及其作用。表达式可以改进很多，但我不打算讨论，因为这不是正确的方法。正如Qtax在评论中指出的那样，您确实应该使用适当的JS minifier来完成此任务。你可能想去看看——它看起来很整洁

如果你仍然不知道它是如何工作的，不要担心。一开始学习正则表达式可能很困难。我建议你使用这个网站-。这是学习正则表达式的一个相当不错的资源。如果你正在找一本书，你可能想看看Jeffrey Friedl写的。
回答2：是的，使用合适的JS迷你版。谷歌是我上次检查的最好的一个。回答2：是的，使用一个合适的JS浏览器。谷歌是我最后检查过的最好的一个。