With TypeScript 1.4, Microsoft offers accommodations for ECMAScript and type system improvements to developers.
"In addition to the type system improvements, one of the main goals for the upcoming TypeScript 2.0 release is to fully support the ECMAScript 6 standard. With TypeScript 1.4, we take another step toward this goal," said Microsoft's Jonathan Turner, program manager for the TypeScript team, in a blog post. "In this release, we've added a new ES6 output mode, support for let and const, and support for ES6 template strings."
Type system improvements, meanwhile, include union types, for specifying that a value is one of a number of different types; type aliases, which better document code and improve readability; and const enums, a restricted form of enums. "For heavy uses of enums, it's helpful to have an even more restricted form that we know is safe to always inline. This helps with performance, code size, and with working with cases where the enum aliases themselves may not be exported," said Turner.
Developers can try out improvements in TypeScript 1.4 as part of the Visual Studio 2015 preview, Visual Studio 2013, and the Node Package Manager.