7 Most Useful Regular Expression Snippets

Regular Expressions can make the life of a programmer very easier. With Regular Expressions, validations just melt down to a single line of code in cases where you are ready to write a clumsy code extending around 50 lines. Here I am presenting a list of 7 most useful Regular Expression snippets to help you.

Note : These snippets show the basic usage of regular expressions. Whole range of validations has not been covered. Only the shown formats have been validated. Please add your comments to make them better!

Demo:

Validate file :


Validate email :


Validate date :


Validate IP :


Validate Number :


Validate Time : (HH:MM or HH:MM:SS or HH:MM:SS.mmm)


Validate Zip : (12345 or 12345-6789)

1. Validating File Name and Extension

function validate_filename(str)
{
 str = str.replace(/^\s|\s$/g, ""); //trims string
 return /^([\w-_]+)\.(asp|html|htm|shtml|php|txt)$/.test(str)
}

2. Validating an Email Address

function validate_email(str) {
    return /^([\w-_.]+)(\.[\w-_.]+)*@([\w\-]+)(\.[\w]{2,7})(\.[a-z]{2})?$/i.test(str);
}

3. Validating a Number

function  validateNumeric( str ) {
  return objRegExp  =  /(^-?\d\d*\.\d*$)|(^-?\d\d*$)|(^-?\.\d\d*$)/.test(str);

}

4. Validating Date (mm/dd/yyyy)

function validate_date(str) {
    return /(?:0[1-9]|[12][0-9]|3[01])\/(?:0[1-9]|1[0-2])\/(?:19|20\d{2})/.test(str);
}

5. Validating Time (HH:MM or HH:MM:SS or HH:MM:SS.mmm)

function validate_time(str) {
    return /^([1-9]|1[0-2]):[0-5]\d(:[0-5]\d(\.\d{1,3})?)?$/.test(str);
}

6. Validating IP Address

function validate_ip(str) {
    return  /^([1-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])(\.([0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])){3}$/.test(str);
}

7. Validating Zip Code(12345-6789)

function validate_zip(str) {
    return  /(^\d{5}$)|(^\d{5}-\d{4}$)/.test(str);
}