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In this article, we will see some of the useful regular expressions which you can use in your real-world applications
^[^@ ]+@[^@ ]+\.[^@ \.]{2,}$
^[^@ ]+ => starts with the character which is not @ and space (one or more occurrence of character)
@[^@ ]+ => then one single @ symbol and after that no @ symbol and no space allowed(one or more occurrence of character)
\.[^@ \.]{2,}$ => then one dot and then at least 2 characters which does not include @, space and dot.
function isEmailValid(email) {
if(/^[^@ ]+@[^@ ]+\.[^@ \.]{2,}$/.test(email)) {
console.log('email is valid');
} else {
console.log('email is invalid')
}
}
isEmailValid('abc@11gmail.com'); // email is valid
isEmailValid('abc11gmail.com'); // email is invalid
(?=.*\d)(?=.*[a-z])(?=.*[A-Z])(?!.*\s)(?=.*[!@#$*])
This regular expression checks for a Password which should contain at least one uppercase letter, lowercase letter, digit, and special symbol
(?=.*\d) => checks for something followed by zero or more occurrence of digit
(?=.*[a-z]) => checks for something followed by zero or more occurrence of lowercase letter
(?=.*[A-Z]) => checks for something followed by zero or more occurrence of uppercase letter
(?!.*\s) => checks for something which is non-space character
(?=.*[!@#$*]) => checks for something followed by zero or more occurrence of special characters from the list !, @, #, $ and *
function isPasswordValid(password) {
if(/(?=.*\d)(?=.*[a-z])(?=.*[A-Z])(?!.*\s)(?=.*[!@#$*])/.test(password)) {
console.log('password is valid');
} else {
console.log('password is invalid')
}
}
isPasswordValid('Abc@123'); // password is valid
isPasswordValid('Abc123'); // password is invalid
\d{4}-\d{2}-\d{2}
This regular expression checks if a date is entered in YYYY–MM–YY format
Like 2019–12–18 i.e 4 digits–2 digits–2 digits
function isDateValid(date) {
if(/\d{4}-\d{2}-\d{2}/.test(date)) {
console.log('date is valid');
} else {
console.log('date is invalid')
}
}
isDateValid('2019-12-18'); // date is valid
isDateValid('2019-2-18'); // date is invalid
^\s*$
This regular expression checks to see if the string contains only spaces
function isEmpty(value) {
if(/^\s*$/.test(value)) {
console.log('string is empty or contains only spaces');
} else {
console.log('string is not empty and does not contain spaces')
}
}
isEmpty('abc'); // string is not empty and does not contain spaces
isEmpty(''); // string is empty or contains only spaces
^[\\(]\d{3}[\\)]\s\d{3}-\d{4}$
This regular expression checks for a phone number in the format (123) 456–8911 i.e (3 digits)(space)(3 digits)(hyphen)(4 digits)
function isValidPhone(phone) {
if(/^[\\(]\d{3}[\\)]\s\d{3}-\d{4}$/.test(phone)) {
console.log('phone number is valid');
} else {
console.log('phone number is invalid')
}
}
isValidPhone('(123) 456-8911'); // phone number is valid
isValidPhone('(123)456-8911'); // phone number is invalid
Visa Credit Card: ^4[0–9]{12}(?:[0–9]{3})?$
American Express Credit Card: ^3[47][0–9]{13}$
Mastercard: ^(?:5[1–5][0–9]{2}|222[1–9]|22[3–9][0–9]|2[3–6][0–9]{2}|27[01][0–9]|2720)[0–9]{12}$
Discover Card: ^6(?:011|5[0–9]{2})[0–9]{12}$
function isValidVisaCard(cardNumber) {
if(/^4[0-9]{12}(?:[0-9]{3})?$/.test(cardNumber)) {
console.log('valid visa credit card number');
} else {
console.log('invalid visa credit card number')
}
}
isValidVisaCard('4111111111111'); // valid visa credit card number
isValidVisaCard('2111111111111'); // invalid visa credit card number
isValidVisaCard('411111111111'); // invalid visa credit card number
If you have difficulty understanding any of the above regular expressions, check out my this article regarding how to easily understand any regular expression in the world.
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