TypeScript 5.3 arrives with assist for import attributes

TypeScript 5.3, an improve to Microsoft’s strongly typed JavaScript variant that provides assist for import attributes for ECMAScript modules, is now obtainable as a manufacturing launch.

TypeScript 5.3 additionally gives options starting from secure assist for decision mode in import varieties to interactive inlay hints for varieties. Introduced November 20, the manufacturing launch will be accessed by NuGet or NPM. The NPM command:

npm set up -D typescript

TypeScript 5.3 backs the most recent updates to the ECMA import attributes proposal. The ECMA proposal introduces an inline syntax for module import statements to go info alongside the module specifier. These attributes will assist further forms of modules in a typical means throughout JavaScript environments, starting with JSON modules.

Microsoft mentioned one use case of import attributes was to offer details about the anticipated format of a module at runtime. In an instance cited, Microsoft mentioned the contents of attributes weren’t checked by TypeScript as a result of they’re host-specific and left alone in order that browsers and runtimes can deal with them.

Import attributes are an evolution an earlier proposal, import assertions, that have been applied in TypeScript 4.5 in November 2021. The obvious distinction is using the with key phrase over the assert key phrase. A much less seen distinction is that runtimes now can use attributes to information the decision and interpretation of import paths, whereas import assertions solely may assert some traits after loading a module. Plans name for deprecating the outdated syntax for import assertion in favor of the proposed normal for import attributes.

TypeScript 5.3 additionally provides an choice to choose type-only auto-imports when potential. Beforehand, when TypeScript generated auto-imports for one thing in a kind place,  it might add a kind modifier based mostly on the developer’s settings. With a latest change, TypeScript now permits an editor-specific choice.

The manufacturing launch follows a beta launch printed October 3 and a launch candidate printed November 3. Predecessor TypeScript 5.2 was launched August 24.

Different new options and enhancements in TypeScript 5.3:

• TypeScript 5.3 helps the resolution-mode attribute for import sort.
• Narrowing will be carried out based mostly on circumstances in every case clause with a swap (true).
• TypeScript 5.3 extra carefully inspects tremendous property accesses and technique calls to see in the event that they correspond to class fields. In the event that they do, a type-checking error will consequence.
• TypeScript inlay hints now assist leaping to the definition of varieties, making it simpler to casually navigate code.
• When operating TypeScript by way of tsc, the compiler will keep away from parsing JSDoc, lowering parsing time and reminiscence utilization to retailer feedback together with time spent in rubbish assortment.
• Consolidation has been achieved between tsserverlibrary.js and typescript.js.
• In JavaScript it’s potential to override the conduct of the instanceof operator. To do that, the worth on the fitting of the operator should have a selected technique named by Image.hasInstance. To raised mannequin this conduct in instanceof, TypeScript now checks if such a [Symbol.Instance] technique exists and is said as a kind predicate operate. If that’s the case, the examined worth on the left facet of the instanceof operator might be narrowed appropriately by that sort predicate.