TypeScript 5.5, the newest model of Microsoft’s strongly typed JavaScript variant, has graduated to a launch candidate (RC) stage. The replace, which brings enhancements starting from efficiency and measurement optimizations to common expression checking, just lately added assist for ECMAScript’s new Set strategies.
The TypeScript 5.5 launch candidate was launched June 6 and may be accessed by way of Nuget or the next command: npm -D typescript@rc. A beta launch was launched April 25 and the ultimate launch is deliberate for June 18.
Since the beta, TypeScript 5.5 added assist for the new Set strategies proposed for JavaScript. Some of those strategies, comparable to union, intersection, and distinction, take one other Set and return a brand new Set because the consequence. Other strategies, comparable to isSubsetOf, take one other Set and return a boolean.
Also new within the launch candidate, TypeScript’s common expression checking has been made barely extra lenient whereas nonetheless erroring on questionable escapes which are allowed solely per ECMAScript’s Annex B. The TypeScript 5.5 (RC) additionally options extra efficiency optimizations, together with skipped checking in transpileModule and optimizations in filtering contextual sorts that may result in sooner construct and iteration instances.
TypeScript 5.5 consists of quite a few different enhancements that have been beforehand accessible within the beta launch. For efficiency and measurement, monomorphization work has been achieved for the language service and public API. With monomorphism, the editor expertise and construct instruments utilizing the TypeScript API will get sooner, TypeScript’s authors mentioned. This was the identical work beforehand achieved for Node and Symbol objects in TypeScript 5.zero to make sure they’d a constant set of properties with a constant initialization order.
TypeScript 5.5 additionally includes a important discount in general package deal measurement. The disk footprint has been diminished from 30.2 MB to 20.four MB, and the packed measurement from 5.5 MB to three.7 MB. As a part of work to allow isolatedDeclarations, Microsoft has improved how usually TypeScript can immediately copy enter supply code when producing declaration recordsdata.
TypeScript 5.5 introduces primary syntax checking on common expressions. Until now, TypeScript sometimes passed over most common expressions in code, as a result of common expressions technically have an extensible grammar and TypeScript by no means made an effort to compile common expressions to earlier variations of JavaScript. This meant frequent issues would go…
