如何理解这个正则表达式？

Question

请有人请说明这个正则表达式......看起来很难理解......

/^[0-9]{1,}((\.){1}[0-9]{1,}){0,1}$/.test(value)

值是我从文本框发送的内容以验证...

Answer 1

^           // start with
[0-9]{1,}   // one or more of 0-9
(
  (\.){1}   // a period
  [0-9]{1,} // one or more of 0-9 
){0,1}      // zero or one of this group
$           // until end

甚至更短：

^[0-9]+((\.)[0-9]+)?$

即。一系列数字，可选地后跟一个句号字符和一系列数字。

所以像

一样

0011221100
12345
1.23456
0.0
0000.1111

将匹配。

Answer 2

编辑：操作不同，所以我更新了解释。

简单地说：

    "
^           # Assert position at the beginning of the string
[0-9]       # Match a single character in the range between “0” and “9”
   {1,}        # Between one and unlimited times, as many times as possible, giving back as needed (greedy)
(           # Match the regular expression below and capture its match into backreference number 1
   (           # Match the regular expression below and capture its match into backreference number 2
      \.          # Match the character “.” literally
   ){1}        # Exactly 1 times
   [0-9]       # Match a single character in the range between “0” and “9”
      {1,}        # Between one and unlimited times, as many times as possible, giving back as needed (greedy)
){0,1}      # Between zero and one times, as many times as possible, giving back as needed (greedy)
\$           # Assert position at the end of the string (or before the line break at the end of the string, if any)
"

编辑2：

你可能想要写这样的正则表达式：

^\d+((\.)+\d+)?$

完全与原始版本具有相同的含义，它当然更具可读性和紧凑性。

编辑3：

要考虑之前的可选整数部分。只需将量词从{1，}更改为{0，}，即从+到*：

^\d*((\.)+\d+)?$