TypeScript 3.3 released: Innovations to Union Types and Build Behavior

TypeScript 3.3 is here. Two new features and an update for the TypeScript plug-in for Sublime Text are included. What changes for developers?

TypeScript 3.3 brings two new features to already known features. On the one hand, the calling behavior of Union Type has been changed and, on the other hand, work has been done on builds that are executed with watch mode. In addition, the TypeScript Sublime Text plug-in now lets you manipulate JavaScript files.

TypeScript 3.3: two changed features

For Union Types, the call behavior has been changed. So far, this has been too restrictive in some cases, according to Rosenwasser. Although the previous behavior for the call of properties did work, but not for types, if the signatures of the types only partially overlapped. Also the common value could not be called as Union Type. That has now been changed. Under what conditions the new behavior can be used and when it is not available, Rosenwasser explains in the blog post for the release of TypeScript 3.3.

A change to the build behavior of the –watch mode is the second new feature. Although the –watch mode was specifically designed to create incremental builds that include only files that have changed or whose dependencies are type checking This did not happen when using –build –watch . This has now been changed in TypeScript 3.3. Tests by the TypeScript team have reduced the build time for incremental builds by 50 to 75 percent over the original build.

Sublime text plug-in

Except from the new release of Typescipt, now you can install the Sublime text plug-in where you can have more accurate completions, renames, go-to-definition and more in JavaScript code that utilizes JSDoc.

For more information about Typescript you can visit the official blog post or the GitHub change log

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