SharePoint Form Validation

Do form validation when you create or edit a list item in a form; Provide standard validation methods like Require, Compare, Regular Expression etc

Features: SharePoint List field data can have simple validations on the server side when a form is submitted. Things like «required field» are the simple kind of validation that can be done. Usually you`d need better validation of input fields. For example if a invalid date is submitted in fields like "star date" and "end date", user needs to notified that start date cannot be later than the end date. This can happen when the submitter creates a task and inputs data in a SharePoint task list form. This application can set up such validation rules and help administrators manage such situations. You can use validations on almost all kinds of lists and most columns. There are some standard validations which can be set with validation values and bounds. These types are "required", "compare", "regular expressions" and "range" validation etc. You just check if you need the "required" validation. This is set when a specific field should not be null. You can specify the error message user sees when the validation violation happens. Regular expression validator requires to be turned on and the regular expression and the error message are to be specified. Range validator needs the minimum and the maximum acceptable values and the error message of course. In the compare validation you need to specify the data type the type of comparison to be done, value to be compared with and the column to be compared, as usual specify the error message string.

Overall: Addressed at a very specific function it adds to the functionality of the standard SharePoint functionality and does it simply and well.

Check whether the user has entered or selected value;
Check whether input value is against a regular expression;
Check whether input value is between two fixed values;
List frequently-used regular expressions in setting pages.
SharePoint Form Validation supports a client-side validation for SharePoint list field data. SharePoint Form Validation provides 4 standard validation types for input content check when users create a SharePoint list item in New-Form or edit an item in Edit Form. They are Required Validation, Regular Expression Validation, Compare Validation, and Range Validation.
Administrator can configure above four validations and customize warning error messages for most columns in a list. Required Field Validator is used for setting whether some column should not be null. Regular Expression Validator is used to check whether inputted content is against a regular expression. Range Validator makes effect when it is required that some value of data should be in a range. Compare Validator plays an important role when data are set to be compared with each other.
By default, SharePoint can do some simple validations to SharePoint list field data such as "Required Field" on server side when you submit form. But users often need list field data validations of various kinds on client side. For instance, when submitter creates a task and input data in a SharePoint task list form, administrator may want him to be noticed on the client side if the data of "Start Date" column is later than "End Date" column. In such a case, SharePoint Form Validation can help administrators achieve it.
SharePoint Form Validation can be used on almost all kinds of lists. For most columns in a list, users can apply standard validation methods such as "Required Validation", "Compare Validation", "Regular Expression Validation" and "Range Validation" on columns.