TypeScript 5.9 supports deferred module evaluation

The preview of the expandable hovers feature, meanwhile, offers “quick info verbosity.” Developers using an editor like Visual Studio Code now will now see + and – buttons on the left of these hover tooltips. Clicking on the + button will expand out types more deeply, while clicking on the – button will return to the previous view, according to Microsoft.

Also in TypeScript 5.9, the language server supports a configurable hover length, which can be configured in VS Code via the js/ts.hover.maximumLength setting. This addresses a situation in which quick info tooltips become so long that TypeScript will truncate them to make them more readable.

Other features in TypeScript 5.9: