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Diffstat (limited to 'docs/getting_started')
| -rw-r--r-- | docs/getting_started/typescript.md | 25 |
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diff --git a/docs/getting_started/typescript.md b/docs/getting_started/typescript.md index 7689273db..265911d51 100644 --- a/docs/getting_started/typescript.md +++ b/docs/getting_started/typescript.md @@ -14,6 +14,31 @@ import { Response } from "https://deno.land/std@0.53.0/http/server.ts"; import { queue } from "./collections.ts"; ``` +### `--no-check` option + +When using `deno run`, `deno test`, `deno cache`,`deno info`, or `deno bundle` +you can specify the `--no-check` flag to disable TypeScript type checking. This +can significantly reduce the time that program startup takes. This can be very +useful when type checking is provided by your editor and you want startup time +to be as fast as possible (for example when restarting the program automatically +with a file watcher). + +Because `--no-check` does not do TypeScript type checking we can not +automatically remove type only imports and exports as this would require type +information. For this purpose TypeScript provides the +[`import type` and `export type` syntax](https://www.typescriptlang.org/docs/handbook/release-notes/typescript-3-8.html#type-only-imports-and-exports). +To export a type in a different file use +`export type { AnInterface } from "./mod.ts";`. To import a type use +`import type { AnInterface } from "./mod.ts";`. You can check that you are using +`import type` and `export type` where necessary by setting the +`importsNotUsedAsValues` TypeScript compiler option to `"error"`. You can see an +example `tsconfig.json` with this option +[in the standard library](https://github.com/denoland/deno/blob/master/std/tsconfig_test.json). + +Because there is no type information when using `--no-check`, `const enum` is +not supported because it is are type-directed. `--no-check` also does not +support the legacy `import =` and `export =` syntax. + ### Using external type definitions The out of the box TypeScript compiler though relies on both extension-less |