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76 lines
2.3 KiB
Markdown
76 lines
2.3 KiB
Markdown
## Location API
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Deno supports the
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[`location`](https://developer.mozilla.org/en-US/docs/Web/API/Window/location)
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global from the web. Please read on.
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### Location flag
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There is no "web page" whose URL we can use for a location in a Deno process. We
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instead allow users to emulate a document location by specifying one on the CLI
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using the `--location` flag. It can be a `http` or `https` URL.
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```ts
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// deno run --location https://example.com/path main.ts
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console.log(location.href);
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// "https://example.com/path"
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```
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You must pass `--location <href>` for this to work. If you don't, any access to
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the `location` global will throw an error.
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```ts
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// deno run main.ts
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console.log(location.href);
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// error: Uncaught ReferenceError: Access to "location", run again with --location <href>.
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```
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Setting `location` or any of its fields will normally cause navigation in
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browsers. This is not applicable in Deno, so it will throw in this situation.
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```ts
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// deno run --location https://example.com/path main.ts
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location.pathname = "./foo";
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// error: Uncaught NotSupportedError: Cannot set "location.pathname".
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```
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### Extended usage
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On the web, resource resolution (excluding modules) typically uses the value of
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`location.href` as the root on which to base any relative URLs. This affects
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some web APIs adopted by Deno.
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#### Fetch API
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```ts
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// deno run --location https://api.github.com/ --allow-net main.ts
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const response = await fetch("./orgs/denoland");
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// Fetches "https://api.github.com/orgs/denoland".
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```
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The `fetch()` call above would throw if the `--location` flag was not passed,
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since there is no web-analogous location to base it onto.
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#### Worker modules
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```ts
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// deno run --location https://example.com/index.html --allow-net main.ts
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const worker = new Worker("./workers/hello.ts", { type: "module" });
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// Fetches worker module at "https://example.com/workers/hello.ts".
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```
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### Only use if necessary
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For the above use cases, it is preferable to pass URLs in full rather than
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relying on `--location`. You can manually base a relative URL using the `URL`
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constructor if needed.
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The `--location` flag is intended for those who have some specific purpose in
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mind for emulating a document location and are aware that this will only work at
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application-level. However, you may also use it to silence errors from a
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dependency which is frivolously accessing the `location` global.
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