Explanation of regular expression

• \s - \s matches any whitespace character
• . - match any character
• • • matches the previous token between one and unlimited times.
• ^ - asserts position at start of a line
• \w - matches any word character (equivalent to [a-zA-Z0-9_])
• \d - matches a digit (equivalent to [0-9])
• \w+@(?:google.\com) - ?: this represents to turn capture group off

⌈colou?r⌋ - The metacharacter ⌈?⌋ (question mark) means optional.

Command	Description
\d	Match for a single digit
\D	Do not match \d
\w	Match for a single letter or digit (0-9 or a-z or A-Z)
\W	Do not match \w
\s	Match a single space (space, tab, newline characters included)
\S	Do not match \s
[A-D]	Match a single character in the A-D range
[^A-D]	Don't match a single character in the A-D range
.	A single wildcard
?	Match previous character 0 or 1 time
*	Match previous character 0 or more times
+	Match previous character 1 or more times
{3}	Match previous character 3 times
{1,3}	Match previous character between 1 and 3 times
^	Beginning of a string
$	End of a string
[]	Match characters in this bracket range
[^]	Don't match characters in this range
`	`
()	Capture groupings
(?:)	Turns capture groupings function off

pattern	Description
4?986	Here the 4 is optional but now you see we are matching on anything that either has 4 or doesn't have it.
a{2, 4}	matching 2 or 3 or 4 times but not matching one time.

match 6 digit number

const numberPattern = /\d{6}/gm;
return numberPattern.test(123456);

match a single character 3 times

const numberPattern = /[a]{3}/gm;
'aaah, this is practice place'.match(numberPattern);

match start with H and end with !

const numberPattern = /^H.+!/gm;
'Hello world! This is regex.'.match(numberPattern);

match a single character in the range between a and h

const numberPattern = /[a-h]/gm;
'aaah, this is practice place'.match(numberPattern);

match a single character either a or h

const numberPattern = /[a|h]/gm;
'aaah, this is practice place'.match(numberPattern);

Get only numbers from the string.

const numberPattern = /\d+/g;
'something102asdfkj1948948'.match(numberPattern);

Get array from the href

const reURLInformation = new RegExp(
    [
        "^(https?:)//", // protocol
        "(([^:/?#]*)(?::([0-9]+))?)", // host (hostname and port)
        "(/{0,1}[^?#]*)", // pathname
        "(\\?[^#]*|)", // search
        "(#.*|)$" // hash
    ].join("")
);
const match = item.url.match(reURLInformation);

Email Validation

const re = /^\S+@+\S+\.+\S+/;
return re.test('a@gmail.com');

const emailReg = RegExp(
    /^(([^<>()\[\]\\.,;:\s@"]+(\.[^<>()\[\]\\.,;:\s@"]+)*)|(".+"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/gm
);
if (!emailReg.test(email)) {}

Email Validation 2

const re = /^(\S+)@([a-zA-Z]+\.(com|org|edu|gov))$/;
return re.test('a@gmail.com');

const emailReg = RegExp(
    /^(([^<>()\[\]\\.,;:\s@"]+(\.[^<>()\[\]\\.,;:\s@"]+)*)|(".+"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/gm
);
if (!emailReg.test(email)) {}

Phone Varification

const re = /^[(][0-9]{3}[)][0-9]{3}-[0-9]{4}/;
return re.test(9033558036);

Phone Varification xxx-xxx-xxxx pattern

const re = /d{3}-\d{3}-\d{4}/;
return re.test(903-355-8036);

Phone number with minimal false positives

const re = /^(?:\+1[-. ]?)?(?:\(?([0-9]{3})\)?[-. ]?)?([0-9]{3})[-. ]?([0-9]{4})$/gm;
return re.test(903-355-8036);

Username must be between 4-12 characters & Can only contain letters, numbers, dashes or underscores

    const usernameReg = RegExp(/^[a-z0-9_-]{4,12}$/);
    if (!usernameReg.test(username)) {}

Password must contain a minimum eight characters, at least one letter and one number

    const passwordReg = RegExp(/^(?=.*[A-Za-z])(?=.*\d)[A-Za-z\d]{8,}$/);
    if (!passwordReg.test(password)) {}

Meta character matching (match five characters with space)

const re = /\w{5}\s\w{5}\!/;
return re.test('Hello World!');

To match the start and of the string

const re = /^Hello World!$/;
return re.test('Hello World!');

To match ip address

const re = /\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}/;
return re.test('192.168.1.1');

To match ip address using drouping

const re = /(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})/;
return re.test('192.168.1.1');