Microsoft, Igalia, and Bloomberg have initiated a proposal to include syntax for explicit type definitions in the JavaScript specification, similar to the syntax used in TypeScript. Currently, the prototype changes proposed for inclusion in the ECMAScript standard are under preliminary discussion (Stage 0). At the upcoming March meeting of the TC39 committee, it is planned to transition to the first stage of proposal consideration with the involvement of the expert community from ECMA.
Having explicitly defined type information will help to avoid many errors during development, allow for additional optimization techniques, simplify debugging, and make code more readable and easier for third-party developers to enhance and maintain. Type support is proposed as an optional feature—JavaScript engines and runtimes that do not support type checking will ignore type annotations and process the code as before, treating type information as comments. However, type-checking tools will be able to identify errors related to improper type usage based on the available information.
Unlike type information defined through JSDoc annotations provided in comment form, directly specifying types in variable definition constructs will make the code more visual, understandable, and easier to edit. For example, integrated development environments that support TypeScript will be able to immediately highlight errors in typed JavaScript code without additional transformations. Furthermore, built-in type support will enable the execution of programs written in typed dialects of JavaScript, such as TypeScript and Flow, without the need for transpilation from one language to another.
Из типов предлагается добавить «string», «number» и «boolean», которые можно будет использовать при определении переменных, параметров функций, элементов объектов, полей классов, типизированных массивов («number[]»). Предлагается также обеспечить поддержку объединённых типов («string | number») и дженериков. let x: string; function add(a: number, b: number) { return a + b; } interface Person { name: string; age: number; } function foo<T>(x: T) { return x; } function foo(x: string | number): string | number { if (typeof x === number) { return x + 1 } else { return x + «!» } }
Source: opennet.ru
