Regular expression to remove substring with known start and end pattern, with multiple words in betw-CodePudding

This is the example substring I'm trying to remove:

On Feb 4, 2018 11:00 PM,

Problem is it can appear multiple times in a string. I just want to remove it/replace with nothing eg. ''.

You could do this a lazy way where you know the length of the pattern, substring it.

I have tried a regex like this:

str.replaceAll(/^On*PM,$/g, '')

Where the ^ and $ indicate start end... I'm missing the space/multiple words.

The months/time are dynamic but not that many combinations.

CodePudding user response：

Use

/\bOn\s (?:Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sept?|Oct|Nov|Dec)\s (?:0?[1-9]|[12]\d|3[01]),\s*\d{4}\s*(?:0?[0-9]|1[0-2]):[0-5]?[0-9]\s*[AP]M,/gi

See regex proof.

EXPLANATION

--------------------------------------------------------------------------------
  \b                       the boundary between a word char (\w) and
                           something that is not a word char
--------------------------------------------------------------------------------
  On                       'On'
--------------------------------------------------------------------------------
  \s                       whitespace (\n, \r, \t, \f, and " ") (1 or
                           more times (matching the most amount
                           possible))
--------------------------------------------------------------------------------
  (?:                      group, but do not capture:
--------------------------------------------------------------------------------
    Jan                      'Jan'
--------------------------------------------------------------------------------
   |                        OR
--------------------------------------------------------------------------------
    Feb                      'Feb'
--------------------------------------------------------------------------------
   |                        OR
--------------------------------------------------------------------------------
    Mar                      'Mar'
--------------------------------------------------------------------------------
   |                        OR
--------------------------------------------------------------------------------
    Apr                      'Apr'
--------------------------------------------------------------------------------
   |                        OR
--------------------------------------------------------------------------------
    May                      'May'
--------------------------------------------------------------------------------
   |                        OR
--------------------------------------------------------------------------------
    Jun                      'Jun'
--------------------------------------------------------------------------------
   |                        OR
--------------------------------------------------------------------------------
    Jul                      'Jul'
--------------------------------------------------------------------------------
   |                        OR
--------------------------------------------------------------------------------
    Aug                      'Aug'
--------------------------------------------------------------------------------
   |                        OR
--------------------------------------------------------------------------------
    Sep                      'Sep'
--------------------------------------------------------------------------------
    t?                       't' (optional (matching the most amount
                             possible))
--------------------------------------------------------------------------------
   |                        OR
--------------------------------------------------------------------------------
    Oct                      'Oct'
--------------------------------------------------------------------------------
   |                        OR
--------------------------------------------------------------------------------
    Nov                      'Nov'
--------------------------------------------------------------------------------
   |                        OR
--------------------------------------------------------------------------------
    Dec                      'Dec'
--------------------------------------------------------------------------------
  )                        end of grouping
--------------------------------------------------------------------------------
  \s                       whitespace (\n, \r, \t, \f, and " ") (1 or
                           more times (matching the most amount
                           possible))
--------------------------------------------------------------------------------
  (?:                      group, but do not capture:
--------------------------------------------------------------------------------
    0?                       '0' (optional (matching the most amount
                             possible))
--------------------------------------------------------------------------------
    [1-9]                    any character of: '1' to '9'
--------------------------------------------------------------------------------
   |                        OR
--------------------------------------------------------------------------------
    [12]                     any character of: '1', '2'
--------------------------------------------------------------------------------
    \d                       digits (0-9)
--------------------------------------------------------------------------------
   |                        OR
--------------------------------------------------------------------------------
    3                        '3'
--------------------------------------------------------------------------------
    [01]                     any character of: '0', '1'
--------------------------------------------------------------------------------
  )                        end of grouping
--------------------------------------------------------------------------------
  ,                        ','
--------------------------------------------------------------------------------
  \s*                      whitespace (\n, \r, \t, \f, and " ") (0 or
                           more times (matching the most amount
                           possible))
--------------------------------------------------------------------------------
  \d{4}                    digits (0-9) (4 times)
--------------------------------------------------------------------------------
  \s*                      whitespace (\n, \r, \t, \f, and " ") (0 or
                           more times (matching the most amount
                           possible))
--------------------------------------------------------------------------------
  (?:                      group, but do not capture:
--------------------------------------------------------------------------------
    0?                       '0' (optional (matching the most amount
                             possible))
--------------------------------------------------------------------------------
    [0-9]                    any character of: '0' to '9'
--------------------------------------------------------------------------------
   |                        OR
--------------------------------------------------------------------------------
    1                        '1'
--------------------------------------------------------------------------------
    [0-2]                    any character of: '0' to '2'
--------------------------------------------------------------------------------
  )                        end of grouping
--------------------------------------------------------------------------------
  :                        ':'
--------------------------------------------------------------------------------
  [0-5]?                   any character of: '0' to '5' (optional
                           (matching the most amount possible))
--------------------------------------------------------------------------------
  [0-9]                    any character of: '0' to '9'
--------------------------------------------------------------------------------
  \s*                      whitespace (\n, \r, \t, \f, and " ") (0 or
                           more times (matching the most amount
                           possible))
--------------------------------------------------------------------------------
  [AP]                     any character of: 'A', 'P'
--------------------------------------------------------------------------------
  M,                       'M,'

Or, simpler one if the strings you deal with are in good shape:

/\bOn\s \w \s \d{1,2},\s*\d{4}\s*\d{1,2}:\d{1,2}\s*[AP]M,/gi

See this proof.

EXPLANATION

--------------------------------------------------------------------------------
  \b                       the boundary between a word char (\w) and
                           something that is not a word char
--------------------------------------------------------------------------------
  On                       'On'
--------------------------------------------------------------------------------
  \s                       whitespace (\n, \r, \t, \f, and " ") (1 or
                           more times (matching the most amount
                           possible))
--------------------------------------------------------------------------------
  \w                       word characters (a-z, A-Z, 0-9, _) (1 or
                           more times (matching the most amount
                           possible))
--------------------------------------------------------------------------------
  \s                       whitespace (\n, \r, \t, \f, and " ") (1 or
                           more times (matching the most amount
                           possible))
--------------------------------------------------------------------------------
  \d{1,2}                  digits (0-9) (between 1 and 2 times
                           (matching the most amount possible))
--------------------------------------------------------------------------------
  ,                        ','
--------------------------------------------------------------------------------
  \s*                      whitespace (\n, \r, \t, \f, and " ") (0 or
                           more times (matching the most amount
                           possible))
--------------------------------------------------------------------------------
  \d{4}                    digits (0-9) (4 times)
--------------------------------------------------------------------------------
  \s*                      whitespace (\n, \r, \t, \f, and " ") (0 or
                           more times (matching the most amount
                           possible))
--------------------------------------------------------------------------------
  \d{1,2}                  digits (0-9) (between 1 and 2 times
                           (matching the most amount possible))
--------------------------------------------------------------------------------
  :                        ':'
--------------------------------------------------------------------------------
  \d{1,2}                  digits (0-9) (between 1 and 2 times
                           (matching the most amount possible))
--------------------------------------------------------------------------------
  \s*                      whitespace (\n, \r, \t, \f, and " ") (0 or
                           more times (matching the most amount
                           possible))
--------------------------------------------------------------------------------
  [AP]                     any character of: 'A', 'P'
--------------------------------------------------------------------------------
  M,                       'M,'