The Windows Library for JavaScript (abbreviated as WinJS) is an open-source JavaScript library developed by Microsoft. It has been designed with the primary goal of easing development of Windows Store apps for Windows 8 and Windows 10, as well as Windows Phone apps for Windows Phone 8.1, Windows 10 Mobile and Xbox One applications using HTML5 and JavaScript, as an alternative to using WinRT XAML and C#, VB.NET or C++ (CX). WinJS started as a technology that was specific to Windows Store apps, but has evolved to aim at working in any Web browser.