SPServices is a jQuery library which abstracts SharePoint's Web Services and makes them easier to use. It also includes functions which use the various Web Service operations to provide more useful (and cool) capabilities. It works entirely client side and requires no server install.
SharePoint's Web Services allow you to interact directly with SharePoint objects such as lists, webs, pages, and permissions without deploying any server-side code. The Web Service operations can be built together into more full-featured functionality that can provide real value to SharePoint users and improve the overall user experience.
SPServices includes not only jQuery "wrappers" for most commonly used Web Services and their operations, but also value-added functions that let you add functionality to forms and pages with very little work.
Some of the most popular value-added functions are:
- $().SPServices.SPCascadeDropdowns - The SPCascadeDropdowns function lets you set up cascading dropdowns on SharePoint forms. What this means is that you can enforce hierarchical relationships between column values, like Site/State or Product Family/Product Code.
- $().SPServices.SPSetMultiSelectSizes - Sets the size of the boxes in a multi-select picker based on the values they contain.
- $().SPServices.SPComplexToSimpleDropdown - Converts a "complex" dropdown (which SharePoint displays if there are 20+ options) to a "simple" dropdown (select).
And many more...