diff --git a/README.md b/README.md index edada8e..db669dc 100644 --- a/README.md +++ b/README.md @@ -291,6 +291,13 @@ const instance = new Test(); type TestTypeFromInstance = Class; ``` +This works with type parameters: +```js +function newInstance(c: Class) { + ... +} +``` + ### TypeScript ```ts @@ -298,6 +305,14 @@ class Test {}; type TestType = typeof Test; ``` +This unfortunately doesn't work with type parameters: +```ts +// error: 'T' only refers to a type, but is being used as a value here.(2693) +function newInstance(c: typeof T) { + ... +} +``` + ## Keys/Props Of Type ### Flow @@ -405,7 +420,7 @@ These are functions that return a boolean, performing some logic to assert that The implementations differ between Flow and TypeScript: -In TypeScript, it ensures the mapping between: `true` and `value is T`, versus in the case of Flow, it ensures the value is "checked" against the logic within the body of the function (i.e. things like `typeof`, `instanceof`, `value === undefined`). +In TypeScript, it ensures the mapping between: `true` and `value is T`, versus in the case of Flow, it ensures the value is "checked" against the logic within the body of the function (i.e. things like `typeof`, `instanceof`, `value === undefined`). This means you cannot tell Flow that the tested parameter is of an arbitrary type, which closes the door to complex cases, e.g.: - reusing logic from a different function @@ -654,7 +669,7 @@ type C = Omit; // C is { b: number } ``` -However, Flow implementation is stricter in this case, as B have a property that A does not have, it would rise an error. In Typescript, however, they would be ignored. +However, Flow implementation is stricter in this case, as B have a property that A does not have, it would rise an error. In Typescript, however, they would be ignored. # Same syntax @@ -683,8 +698,8 @@ This is supported by Flow. And we list out the different syntaxes here: [Try Flo ```js type F = { - (): string, - [[call]]: (number) => string, + (): string, + [[call]]: (number) => string, [[call]](string): string } @@ -719,7 +734,7 @@ Reference: - [Callable Objects](https://flow.org/en/docs/types/functions/#callable-objects-) - [immer.js](https://github.com/immerjs/immer/blob/master/src/immer.js.flow) uses it to overload the `produce` (default export) function which has multiple call signatures -- [Styled Components](https://github.com/flow-typed/flow-typed/blob/master/definitions/npm/styled-components_v4.x.x/flow_v0.75.x-/styled-components_v4.x.x.js#L242) uses it to separate cases of being called on a string and wrapping a component +- [Styled Components](https://github.com/flow-typed/flow-typed/blob/master/definitions/npm/styled-components_v4.x.x/flow_v0.75.x-/styled-components_v4.x.x.js#L242) uses it to separate cases of being called on a string and wrapping a component - [Reselect Library Definition](https://github.com/flow-typed/flow-typed/blob/master/definitions/npm/re-reselect_v2.x.x/flow_v0.67.1-/re-reselect_v2.x.x.js) contains massive chunks of overloaded call properties ### TypeScript