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Regular Expressions in JavaScript

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Excluding Characters

3:13 with Joel Kraft

Matching any character EXCEPT a specific character can be very useful at times. Learn how.

Practice

Copy both the Match and the Exclude set of test strings from each exercise below into a Regex tester like RegEx Pal or regex101. Using what you've learned so far, create a regular expression that will match all of the strings in the Match set and exclude the ones in the Exclude set.

1 )
Match:
foxes
jumping
dogs
Exclude:
aaaaa

2 )
Match:
34522
72379
Exclude:
1234k
5784k
5784k

3 )
Match *only* the commas:
pears,
apples,
cherries,
oranges,

4 )
Match only the text character strings from each line ('html', 'head', etc):
<html>
<head>
</head>
<body>
<div>
</div>
</body>
</html>

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    You can exclude any character or characters from a match. 0:00
    This can be useful for matching text between delimiters. 0:04
    For comma separated values, for example, 0:08
    we could match any character that is not a comma to pull delimited values out. 0:11
    To match any character, 0:16
    except a target character, we'll use a character set that starts with caret. 0:18
    For example, to match any character except an @ symbol, 0:23
    you can put an @ symbol next to a caret in a character set. 0:26
    Add a dot to that to exclude dots from what's matched. 0:30
    Let's try it out. 0:34
    I cleared both windows out so we can start with a new example. 0:35
    Let's put an email address in as test. 0:39
    Say, toy@boat.com. 0:42
    Now I'll match any character that's not an @ symbol. 0:47
    I'll put square brackets with a caret and inside I'll put an @ symbol. 0:51
    The striping means that each character is a separate complete match for 0:57
    our expression, every character except the @ symbol that is. 1:01
    If we want to match more than one character with our expression, 1:05
    what should we do? 1:09
    Do you remember? 1:10
    One way would be to put a + sign after it. 1:11
    Now we have two complete matches. 1:14
    The parser found three characters that were not @ symbols. 1:17
    Then it found an @ symbol, so toy is the first match for this expression. 1:20
    After the @ symbol, 1:26
    it found boat.com was a repeated string of characters that weren't @ symbols. 1:27
    If I put a dot in the set, you see the string has three complete matches. 1:33
    There are a couple gotchas I want to point out here. 1:39
    Notice that a dot inside a set behaves differently than a dot outside a set. 1:42
    Inside, it's a literal dot, while outside, 1:48
    it's a special character that matches everything. 1:51
    This can take some getting used to, but just remember context matters. 1:54
    Next, think about what would happen if I remove the + and 1:59
    put an m before the character set. 2:03
    Do you think it will match the m at the end of the string, 2:06
    because m isn't followed by an @ or a dot? 2:09
    Let's find out. 2:12
    Turns out the m is not matched. 2:15
    This is because the m isn't followed by a character at all. 2:17
    The character set is telling the parser that m must be followed by a character, 2:22
    it just can't be an @ symbol or a dot. 2:27
    So if I put a character here, say a % sign, we have a match. 2:30
    Regular expressions include characters which are the opposite of the digit, 2:35
    word and whitespace characters we learned earlier. 2:39
    If you capitalize any of them, you get the inverse. 2:43
    So \D, for example, matches any character that is not a digit. 2:46
    For example, if I erase this regex and put a /W, 2:53
    the @ symbol and dot are matched because they are not word characters. 2:57
    If I put a D instead, each character is matched because none of them are numerals. 3:04
    Check the teacher's notes for additional practice. 3:10

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