Input - pattern : regexp

pattern =" regexp "

Parameters :

regexp -	Specifies a regular expression that the <input> element's value is checked against

Example :

# An <input> element with type="password" that must contain 8 or more characters:
<input type="text" id="country_code" name="country_code" pattern="[A-Za-z]{3}" title="Three letter country code">

# An <input> element with type="password" that must contain 8 or more characters that are of at least one number, and one uppercase and lowercase letter:
<input type="password" id="pwd" name="pwd" pattern=".{8,}" title="Eight or more characters">

# An <input> element with type="email" that must be in the following order: characters@characters.domain (characters followed by an @ sign, followed by more characters, and then a "."
# After the "." sign, add at least 2 letters from a to z:
<input type="email" id="email" name="email" pattern="[a-z0-9._%+-]+@[a-z0-9.-]+\.[a-z]{2,}$">

# An <input> element with type="search" that CANNOT contain the following characters: ' or "
<input type="search" id="search" name="search" pattern="[^'\x22]+" title="Invalid input">

# An <input> element with type="url" that must start with http:// or https:// followed by at least one character:
<input type="url" id="website" name="website" pattern="https?://.+" title="Include http://">

The pattern attribute specifies a regular expression that the <input> element's value is checked against on form submission.

Note: The pattern attribute works with the following input types: text, date, search, url, tel, email, and password.

Tip: Use the global title attribute to describe the pattern to help the user.