It’s not about button mashing, it’s about declarative programming. You don’t know it yet, but you want to use Regexes, and you want other people around you to use Regexes, too. I’ll tell you how they work, why they are the best thing since higher-order functions, and how to use them right. You’ll love it!

2. @listochkin
CTO at Viravix

4. xkcd
2005

10. A language for text
manipulations

11. Regular Expressions

14. Used them to describe math of
events in neural networks

15. SDS 940
1966 - QED
1968 - Mother of All Demos
1969 - 1st ARPANET IMP node

16. 1966 - Ken Thompson QED
1986 - Henry Spencer regex
1997 - Philip Hazel PCRE

18. /(.*)?//.+[^z]{1,}1(bw+)s?/

25. Quiz Time!

26. s = s[4] === 's' ? s.substr(8) : s.substr(7);
const iQ = s.indexOf('?');
const iH = s.indexOf('#');
const iS = s.indexOf('/');
if (Math.min(iQ, iH, iS) > 0) {
return s.substr(0, Math.min(iQ, iH, iS));
} else {
return s;
}

27. /http[s]?://(?<domain>[^?#/]+)/
.exec(s).groups.domain

28. Math

29. + - * /

30. Trigonometry
Complex numbers
Integration
Derivatives

31. Text

32. substr(3, 5)
indexOf(‘a’)

33. Regular Expressions is like
a higher-level math for text

34. How do regexes work?

35. SQL
CSS selectors
File glob patterns

36. DSL

37. Special VM

38. Statically / JIT compiled

39. Often fast even for “slow”
languages

40. 2008
JavaScriptCore
Regex JIT

41. $("form.add-product button[type=submit]")
.on("click", function (e) {
...
})

42. /abc/

43. function* enumerate(iterable) {
let i = 0;
for (const x of iterable) {
yield [i, x];
i++;
}
}

44. function matchAbc(string) {
for (const [startPos] of enumerate(string)) {
let matchPos = startPos;
if (str[matchPos] !== 'a') continue;
matchPos += 1;
if (str[matchPos] !== 'b') continue;
matchPos += 1;
if (str[matchPos] !== 'c') continue;
return true;
}
return false;
}

46. ababc

47. ababc

48. ababc

49. ababc

50. function matchAbc(string) {
for (const [startPos] of enumerate(string)) {
let matchPos = startPos;
if (str[matchPos] !== 'a') continue;
matchPos += 1;
if (str[matchPos] !== 'b') continue;
matchPos += 1;
if (str[matchPos] !== 'c') continue;
return true;
}
return false;
}

51. ababc

52. ababc

53. Not smart but predictable

54. Very good for hardware

55. Language

56. Every character is
an instruction

57. Most instructions mean
“Match this exact character,
move forward
by one character
if matched”

58. /abc|abx/

61. Longer to compile
Faster to execute

62. /anteater|antelope|ant/
An ant encountered an anteater

64. /anteater|antelope|ant/
An ant encountered an anteater

66. Put most likely alternative
to the left

67. /x*z/

69. /”.*”/

70. I watched “Home Alone” and
“Back to the Future” last week

71. I watched “Home Alone” and
“Back to the Future” last week

72. I watched “Home Alone” and
“Back to the Future” last week

73. I watched “Home Alone” and
“Back to the Future” last week

74. I watched “Home Alone” and
“Back to the Future” last week

75. I watched “Home Alone” and
“Back to the Future” last week

76. I watched “Home Alone” and
“Back to the Future” last week

77. I watched “Home Alone” and
“Back to the Future” last week

78. I watched “Home Alone” and
“Back to the Future” last week

79. /x*z/

80. /x*?z/

83. /”.*”/

84. /”.*?”/

85. I watched “Home Alone” and
“Back to the Future” last week

86. I watched “Home Alone” and
“Back to the Future” last week

87. I watched “Home Alone” and
“Back to the Future” last week

88. I watched “Home Alone” and
“Back to the Future” last week

89. I watched “Home Alone” and
“Back to the Future” last week

90. I watched “Home Alone” and
“Back to the Future” last week

91. I watched “Home Alone” and
“Back to the Future” last week

92. How to regex

93. DSL

94. Treat regexes as code

95. Step 1. Formatting

96. function (a){function*b(a){let b=0;for(const
c of a)yield[b,c],b++}for(const[c] of b(a))
{let a=c;if("a"===str[a]&&(a+=1,"b"===str[a]
&&(a+=1,"c"===str[a])))return!0}return!1}

97. Use extended formatting!

98. /(d{4})-(d{2})-(d{2})/

99. /(?x)
# ISO date format
d {4}
-
d {2}
-
d {2}
/

102. function r(re, flags = 'u') {
return new RegExp(
re
.replace(/^(?<regex>.*)(?<!)#.*$/gm, '$<regex>')
.replace(/#/gm, '#')
.replace(/s/gm, ''),
flags
);
}

103. r(String.raw`
# ISO date format
d {4}
-
d {2}
-
d {2}
`)

104. Step 2. Naming

105. /http[s]?://(?<domain>[^?#/]+)/
.exec(s).groups.domain

106. /http[s]?://([^?#/]+)/
.exec(s)[1]

107. function r(re, flags = 'u') {
return new RegExp(
re
.replace(/^(?<regex>.*)(?<!)#.*$/gm, '$<regex>')
.replace(/#/gm, '#')
.replace(/s/gm, ''),
flags
);
}

108. function r(re, flags = 'u') {
return new RegExp(
re
.replace(/^(.*)(?<!)#.*$/gm, '$1')
.replace(/#/gm, '#')
.replace(/s/gm, ''),
flags
);
}

109. r(String.raw`
# ISO date format
(?<year> d {4})
-
(?<month> d {2})
-
(?<day> d {2})
`)

110. /http[s]?://(?<domain>[^?#/]+)/
.exec(s).groups.domain

111. r(String.raw`
http[s]? ://
(?<domain> [^?#/]+ )
# rest of the url
`).exec(s).groups.domain

112. Step 3. Structure

113. Perl & PCRE define

114. /(?x)
(?&sign)? (?&mantissa) (?&exponent)?
(?(DEFINE)
(?<sign> [+-] )
(?<mantissa> d++.?+d*+ | . d++ )
(?<exponent> [eE] (?&sign)?+ d++ )
)
/

115. Yes, even recursion

116. /(?x)
(?(DEFINE)
(?<object> { (?&nvp) [, (?&nvp)]* })
(?<nvp> (?&name) : (?&value) )
(?<value>
(?&number) |
(?&boolean) |
(?&string) |
(?&object) |
(?&array)
)
...
)
(?&value)
/

117. JSON parsing Regex

118. use PPR;
my $perl_block = qr{
(?&PerlBlock)
$PPR::GRAMMAR
}x;

119. 1860 lines

120. Отвал башки

123. Raku grammars

124. /
:my regex sign { <[+-]> }
:my regex mantissa {
d+: '.'?: d*: | '.' d+:
}
:my regex exponent { <[eE]> <sign>?: d+: }
<sign>? <mantissa> <exponent>?
/

125. function r(re, flags = 'u') {
return new RegExp(
re
.replace(/^(?<regex>.*)(?<!)#.*$/gm, '$<regex>')
.replace(/#/gm, '#')
.replace(/s/gm, ''),
flags
);
}

126. [2020-09-11T15:57:20.848Z - 099fe80d-7e11-4c47-9bbf-2372bd6b2527: 108ms]
200 OK GET /configuration-tree/8 <- http://web.app.ui/ 178.133.180.67
'Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:82.0)
Gecko/20100101 Firefox/82.0'
{"id":1,"email":"andrei.listochkin@viravix.com",...}

127. [Time in UTC - Request ID: Response Time]
[2020-09-11T15:57:20.848Z - 099fe80d-7e11-4c47-9bbf-2372bd6b2527: 108ms]
Status Code and Message Request Method and Path <- Refer URL User IP
200 OK GET /configuration-tree/8 <- http://web.app.ui/ 178.133.180.67
User Agent
'Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:82.0)
Gecko/20100101 Firefox/82.0'
Session Token
{"id":1,"email":"andrei.listochkin@viravix.com",...}

128. ^
[
(?<requestDate>2020-0[789]S+)
s - s
(S+) # request ID
: s
(?<requestDuration>d+)ms
]
s .+ s
(?<session>S+) (?<!null) # non-anonymous sessions only
$

129. const match = lineRe.exec(logLine);
if (match) {
const { requestDate, requestDuration, session } = match;
const requestData = {
date: new Date(requestDate),
duration: parseInt(requestDuration, 10),
email: JSON.parse(session).email
}
}

130. Regexes are awesome.

131. Üñiçødé aware

132. Advanced “math” on text

133. Declarative

134. Maintainable

136. Your best friend
when it comes
to text processing