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68 lines
1.9 KiB
Markdown
68 lines
1.9 KiB
Markdown
# Module metadata
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## Concepts
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- [import.meta](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/import.meta)
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can provide information on the context of the module.
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- The boolean
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[import.meta.main](https://doc.deno.land/builtin/stable#ImportMeta) will let
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you know if the current module is the program entry point.
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- The string [import.meta.url](https://doc.deno.land/builtin/stable#ImportMeta)
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will give you the URL of the current module.
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- The string
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[Deno.mainModule](https://doc.deno.land/builtin/stable#Deno.mainModule) will
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give you the URL of the main module entry point, i.e. the module invoked by
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the deno runtime.
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## Example
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The example below uses two modules to show the difference between
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`import.meta.url`, `import.meta.main` and `Deno.mainModule`. In this example,
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`module_a.ts` is the main module entry point:
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```ts
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/**
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* module_b.ts
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*/
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export function outputB() {
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console.log("Module B's import.meta.url", import.meta.url);
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console.log("Module B's mainModule url", Deno.mainModule);
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console.log(
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"Is module B the main module via import.meta.main?",
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import.meta.main,
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);
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}
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```
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```ts
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/**
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* module_a.ts
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*/
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import { outputB } from "./module_b.ts";
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function outputA() {
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console.log("Module A's import.meta.url", import.meta.url);
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console.log("Module A's mainModule url", Deno.mainModule);
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console.log(
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"Is module A the main module via import.meta.main?",
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import.meta.main,
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);
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}
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outputA();
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console.log("");
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outputB();
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```
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If `module_a.ts` is located in `/home/alice/deno` then the output of
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`deno run --allow-read module_a.ts` is:
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```
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Module A's import.meta.url file:///home/alice/deno/module_a.ts
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Module A's mainModule url file:///home/alice/deno/module_a.ts
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Is module A the main module via import.meta.main? true
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Module B's import.meta.url file:///home/alice/deno/module_b.ts
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Module B's mainModule url file:///home/alice/deno/module_a.ts
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Is module B the main module via import.meta.main? false
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```
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