Regular Expressions in Javascript

Here are some examples of using regular expressions for input validations in javascript.

var input = “hello222″;
var ok = false;

var dob_regex = /^([0-9]){2}(\/){1}([0-9]){2}(\/)([0-9]){4}$/;   // DD/MM/YYYY
var email_regex = /^[a-zA-Z0-9._-]+@([a-zA-Z0-9.-]+\.)+[a-zA-Z0-9.-]{2,4}$/;  // email address
var username_regex = /^[\w.-]+$/;  // allowed characters: any word . -, ( \w ) represents any word character (letters, digits, and the underscore _ ), equivalent to [a-zA-Z0-9_]
var num_regex = /^\d+$/; // numeric digits only
var search_regex = “/hello/”;
var password_regex = /^[A-Za-z\d]{6,8}$/;  // any upper/lowercase characters and digits, between 6 to 8 characters in total
var phone_regex = /^\(\d{3]\) \d{3}-\d{4}$/;  // (xxx) xxx-xxxx
var question_regex = /\?$/; // ends with a question mark

1. Check that there are at least 3 numeric characters in input
if ( input.match(/d/g) == null ) {
ok = false;
} else if ( input.match(/d/g).length < 3 )  {
ok = false;
} else {
ok = true;
}
2. Check that the input has a minimum of 8 characters
if ( input.length >= 8 ) {
ok = true;
}
3. Check that the input is in a correct date format (DD/MM/YYYY)
if ( dob_regex.test(input) ) {
ok = true;
}
4. Check that the input is in a correct email format (username@example.com)
if ( email_regex.test(input) ) {
ok = true;
}
5. Check that the input matches the specified username format
if ( username_regex.test(input) ) {
ok = true;
}
6. Check that the input contains only numeric characters
if ( input.match(num_regex) ) {
ok = true;
}
7. Search for a specific word in the input
if ( input.search(search_regex) != -1 ) {
ok = true;
}
8. Check that the input matches the specified password format
if ( input.match(password_regex) ) {
ok = true;
}
9. Check that the input matches the specified phone number format
if ( input.match(phone_regex) ) {
ok = true;
}
10. Check that the input is a question (ends with a question mark)
if ( question_regex.test(input) ) {
ok = true;
}