javascript validation formatting requirements

These are the JavaScript validation codes that I came across:

<script type="text/javascript">
function validate_input(form){
   username_pattern=/^[a-zA-Z0-9\_\-]{6,100}$/;
   if (!username_pattern.test(form.username.value)){
      alert ('Username must be at least 6 characters long and can only contain letters or numbers!');
      form.username.focus();
      return false;
   }
return (true);
}
</script>

I have a question regarding this part:

username_pattern=/^[a-zA-Z0-9\_\-]{6,100}$/;

Can anyone explain how to interpret this type of format? Does it specify letters, numbers, or special characters?

javascript

Answer №1

/^[a-zA-Z0-9\_\-]{6,100}$/;

Translated to English, this regular expression specifies that a string can consist of uppercase or lowercase letters, numbers, underscores, and hyphens. It must be between 6 and 100 characters in length.

Additional information:

The string must begin with a letter, number, underscore, or hyphen.

Answer №2

/^[a-zA-Z0-9\_\-]{6,100}$/

^ indicates the start of the string

[a-zA-Z0-9_-] allows for uppercase and lowercase letters, numbers, underscores, or hyphens.

{6,100} specifies a character length ranging from 6 to 100

$ signifies the end of the string

Answer №3

Tools for exploring and testing Regular Expressions.

1. Explain Regex Patterns

2. RegEx101 Online Tool

3. Debuggex Online Demo

^[a-zA-Z0-9\_\-]{6,100}$

Answer №4

^ serves as an anchor, asserting its position at the beginning of the string

[a-zA-Z0-9\_\-]{6,100} matches a single character from the specified list

{6, 100}: Occurs between 6 and 100 times, as many times as possible while meeting requirements

a-z represents a character in the range between lowercase a and z (case sensitive)

A-Z represents a character in the range between uppercase A and Z (case sensitive)

0-9 represents a character in the range between 0 and 9

\_ matches the underscore character literally

\- matches the dash character literally

$ acts as an anchor, asserting its position at the end of the string.

An alternative regular expression using flags would be:

/^[a-z\d\_\-]{6,100}$/i

Here, \d matches digits (0-9), and the flag i indicates case insensitivity.

This demonstrates how regular expressions work to locate matches:

https://i.sstatic.net/33Wvl.png
(source: gyazo.com)

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