RegEx or regular expression is patterns used to match or locate character combinations in strings. It's commonly used to validate input value.

Use it to vaidate password

I used it in my last post to create Mailchimp registration example. Mailchimp requires the password to have

• one lowercase character
• one uppercase character
• one number
• one special character
• 8 characters minimum

This can be validated with RegEx

if (!password.match(/(?=.\d)(?=.[a-z])(?=.[A-Z])(?=.[!@#$%^&*]).{8}/)) {
    return "error message"
}

• (?=.[a-z]) matches any lowercase character
• (?=.[A-Z]) matches any uppercase character
• (?=.\d) matches any number
• (?=.[!@#$%^&*]) matches any special character
• .{8} at least 8 characters

Other uses

From the edabit javascript challenges

Question

From a given string comprised of uppercase and lowercase characters, detect lowercase characters, extract them and return it as one word.

detectWord("UcUNFYGaFYFYGtNUH") ➞ "cat"

Answer

const detectWord = str => {
  return str.replace(/[A-Z]/g, "")
}

• /[A-Z]/g do a global search for uppercase characters
• replace all uppercase characters with empty string " "
• this leaves us with only lowercase characters

Question

How many D's are in a sentence?

countDs("My friend Dylan got distracted in school.") ➞ 4

Answer

const countDs = str => {
  str.match(/d/gi).length
}

• /d/id match character "d", case insensitive