Microsoft has released a beta of TypeScript 5.6, an update to the strongly typed JavaScript variant that disallows nullish and truthy checks on syntax that never varies on nullishness or truthiness.

The TypeScript 5.6 beta, which follows last month’s production release of TypeScript 5.5, was announced July 26. TypeScript 5.6 can be accessed through NuGet or through NPM by running the npm install -D typescript@beta command.

For disallowed nullish and truthy checks, the compiler now errors when it can syntactically determine that a truthy or nullish check will always evaluate in a specific way. Microsoft said “many, many bugs” could be caught this way. Some expressions still are allowed even if truthy or nullish. Specifically, true, false, 0, and 1 are all still allowed despite always being truthy or falsy.