Getting started with validation

Remarks#

Validation is the process of validating/verifying the user entries against some criteria.

The main purpose is to ensure that the user entries are matching with the policy of the system.

For example, if a site allow visitors below an age of 50, then the validation to ensure the user entered age is less than 50 should be done.

Related : Validation - Wikipedia

Installation or Setup

Detailed instructions on getting validation set up or installed.

Validating a name entered by User

Validating the Name entered by a User contain the following check

Ensure it is not empty
Ensure it contain only alphabets, space and/or dot.

So, the regular expression for this is

^[A-Z][a-z]*(\.?\s?[A-Z][a-z]*)+$

This means

^ -> Should start with
[A-Z] -> the first letter should be capital case
[a-z]* -> the leading letters should be small case (Optional and not applicable for Initials. Ex : J. Doe)
(\.?\s?[A-Z][a-z]*)+ -> A dot (.) and/or a space (” ”), then a capital case and small cases. The last + indicates that this part can repeat many times and at least one time it should be there.
$ end. No further words will be there

Example matching : J. Doe , John Doe, John Doe Doe, John D Doe.

Example in JavaScript

var name = "John Doe";
var noname = "123Abc";
console.log(/^[A-Z][a-z]*(\.?\s?[A-Z][a-z]*)+$/.test(name)); // true
console.log(/^[A-Z][a-z]*(\.?\s?[A-Z][a-z]*)+$/.test(noname)); // false

Validating an age against a range

Let’s take the Range is from 18 to 80.

So, to validate,

We should check that the age is a positive integer.

Then check it should be greater than or equal to 18 and less than or equal to 80.

The test to check whether it is a number or not can be performed by a simple regular expression like

^[0-9]+$

Or even simpler

^\d+$

Then we can check it with range as

if age>=18 && age <=80 return true
else return false

Validating whether the user input contain non alpha numeric character

Sometimes, we have to take input from users which should contain only alpha numeric characters.

For example, lets say a Username system which allow only letters and numbers,

Then this can be done with the following Regular Expression

^[a-zA-Z0-9]+$

^ is restrict the start
[a-zA-Z0-9]+ is the main part which allow only small a-z capital A-Z and numbers with a minimum length of 1 to any extend.
$ restrict the end

This can also done by using

^[\w\d]+$

Here

\w represent the alphabets
\d represent the digits

If we want to restrict the length to maximum 20 charactes,

^[a-zA-Z0-9]{1,20}$

The {1,20} indicate that the length can be between 1 and 20 including both.