https://github.com/chanda-abdul/regex-cheatsheet
Regular Expressions in JavaScript
https://github.com/chanda-abdul/regex-cheatsheet
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Regular Expressions in JavaScript
- Host: GitHub
- URL: https://github.com/chanda-abdul/regex-cheatsheet
- Owner: Chanda-Abdul
- Created: 2021-08-30T02:23:16.000Z (about 4 years ago)
- Default Branch: main
- Last Pushed: 2021-09-01T04:31:25.000Z (about 4 years ago)
- Last Synced: 2025-01-13T16:49:13.060Z (9 months ago)
- Size: 20.5 KB
- Stars: 1
- Watchers: 2
- Forks: 1
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
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README
# RegEx Cheatsheet - Regular Expressions in JavaScript
Regex (Regular Expressions) are a way to search through a string of text in an advanced way
https://regexr.com/ for practice and reference
https://regexone.com/lesson/introduction_abcs
https://www.debuggex.com/cheatsheet/regex/javascript
https://regexcrossword.com/
https://youtu.be/rhzKDrUiJVk to follow along
## Format
starts with `/` ends with `/` everything contained within this is the regEx
### Counting and Special Character Selectors
- `e+` search for multiple strings of `e` i.e. `ee` or `eee` etc.
- `e+a?` search for multiple strings of `e` and optionally search for `a`
- `re*` search for multiple strings of `r` and optionally search for zero or more `e`'s
- `/.at/` or `.` matches anything i.e. `fat` `cat` and `eat`, but will not match a new line
- use `\` to "escape" special characters `\@`
- `\w` to match any word character
- `\W` to match any non-word character
- `\s` to match any form of white space
- `\S` to match any form of non-white space
- `\w{4}` matches any word that is `{4}`characters
- `\w{4,}` matches any word that is `{4}` or more characters
- `\w{4,5}` matches any word that is `{4,}` to `{5}`characters
### Range Selectors
- `/[fc]at/` any three letter `at` word that starts with `f` or `c` i.e. `fat` or `cat`
- `/[a-z]at/` starts with any letter in the range of `a` to `z` and ends with `at` i.e. `fat` `cat` and `eat`
- `[a-z]`
- `[A-Z]`
- `[0-9]`
- `[a-f]`
### Capture Group Selectors
- `\(t|T)he\g` match `the` or `The`
- `\(t|e|r){2,3}\.\g` matches between 2 to 3 of the characters `t` `e` or `r` then a `.`
- `/^The/` matches the beginning of the line only
- `/.\$/` match the end of our statement
### Look-aheads and Look-behinds
- `/(?<=[tT]he)./g` positive look-behind, returns the characters behind `the` or `The`, but doesn't actually capture the character
- `/(?everything that doesn't follow behind `the` or `The`
- `/(?=at)./g` positive look-ahead, returns anything that has an `at` after it
- `/(?!at)./g` look-ahead, returns anything that doesn't have an `at` after it
### Flags
after the end `/` you can add flags
- `/g` or global allows you to match anywhere in the string(multiple matches vs first match)
- `/i` case insensitive
- `/m` multiline
##
````
const reg = /e+/g
const sentence =
"The fat cat ran down the street.
It was searching for a mouse to eat."
reg.test(sentence)
````
## Phone Number Example
````
let isPhoneNumber = /\d{10}/g
let phoneNumber = 1234567890
isPhoneNumber.test(phoneNumber)
isPhoneNumber = /\d{3}-?\d{3}-?\d{4}/g
phoneNumber = "123-456-7890"
isPhoneNumber.test(phoneNumber)
isPhoneNumber = /\d{3}[ -]?\d{3}[ -]?\d{4}/g
phoneNumber = "123 456 7890"
isPhoneNumber.test(phoneNumber)
````
Captures digits of phone number
````
/(\d{3})[ -]?(\d{3})[ -]?\(d{4})/gm
````
Returns group 1,2, and 3
````
$1$2$3
````
change group 1's name to areacode
````
/(?\d{3})[ -]?(\d{3})[ -]?\(d{4})/gm
````
````
phoneNumber = "(123) 456-7890"
/\?(?\d{3}\)?[ -]?(\d{3})[ -]?\(d{4})/gm
````
````
phoneNumber = "+ 1 123 456-7890"
/((\+1)[ -])?\?(?\d{3}\)?[ -]?(\d{3})[ -]?\(d{4})/gm
````
## Email Example
````
const emailRegex = /\S+@\S+\.\S+/
const validEmail = "valid@gmail.com"
const fauxEmail = "invalid,con"
emailRegex.test(validEmail)
emailRegex.test(fauxEmail)
````
## Credit Card Example
````
// const creditCardRegex = //g
const validCreditCard = "1234 5678 9101 1123"
const fauxCreditCard = "abcd 0000 fake 1111 card 2222"
// emailRegex.test(validEmail)
// emailRegex.test(fauxEmail)
````
## Currency Example
> Implement a function that will determine if a string represents a valid currency amount Such strings will have the following properties:
> - [x] The amount must consist of base-10 digits
>>
> - [x] The amount may optionally contain thousands separators using the ',' character.
>>
> - [ ] If thousands separators are present, they must be present at each thousands increment.
>>
> - [x] The amount must be prefixed by the currency symbol. We support US Dollars ($), Euros (€), and Japanese Yen (¥) only.
>>
> - [ ] Negative amounts may be indicated either by a negative sign before the currency symbol or by enclosing the amount (including currency symbol) in parentheses, such as ($450)
>>
> - [ ] Dollar and Euro amounts may contain an amount of cents, represented to exactly two digits of precision.
>>
> - [ ] If a decimal point is present, the cents must be specified
>>
> - [ ] Yen amounts may not contain decimal points
> - Amounts may not contain a leading zero, unless it is zero Dollars or Euros and cents are specified
>>
> - [ ] Any other characters, including leading or trailing whitespace, is invalid
````
const currencyRegex = /[\$\€\¥][0-9]{1,3}(?:,?[0-9]{3})*(\.[0-9]{2}$)?/
currencyRegex.test('$450')//true
currencyRegex.test('-€23')//true
currencyRegex.test('(¥2400)')//true
currencyRegex.test('$4,500.00')//true
currencyRegex.test('€0.25')//true
currencyRegex.test('cat')//false
currencyRegex.test('£25')//false
currencyRegex.test('$45,0')//false*
currencyRegex.test('€350')//false*
currencyRegex.test('(-3.50)')//false
currencyRegex.test('¥120.00')//false*
````