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109 lines
3.4 KiB
Markdown
109 lines
3.4 KiB
Markdown
# NodeJS Loader
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The `system-node.cjs` build adds support for loading modules in NodeJS.
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## Installation
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```sh
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npm install --save systemjs
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# or
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yarn add systemjs
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```
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```js
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const { System, applyImportMap, setBaseUrl } = require('systemjs');
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System.import('file:///Users/name/some-module.js').then(module => {
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console.log("The loaded module", module);
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});
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```
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## Features
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SystemJS creates a global variable `global.System` that loaded modules use by calling `System.register()`. Modules may be loaded either from disk (`file://`) or network (`http://`). A loaded module's code is retrieved and eval'ed.
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Since [Import Maps](/docs/import-maps.md) are usually installed via the DOM, system-node.cjs provides an alternative API `applyImportMap` API to support resolution of bare specifiers.
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Separate instances of SystemJS, each with their own import map and module registry, are supported via the `new System.constructor()` API.
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Additionally, [global loading](/README.md#extras), [module types](/docs/module-types.md), and the [SystemJS Registry API](/docs/api.md#registry) are supported. Other extras, such as the AMD extra, have not been thoroughly tested but are presumed to work.
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Modules loaded over HTTP will be loaded via [node-fetch](https://github.com/node-fetch/node-fetch).
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## API
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### System
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A reference to the global SystemJS instance. This is referentially equal to `global.System`.
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```js
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const { System } = require('systemjs');
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console.log(System === global.System) // true
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System.import('file:///Users/name/some-module.js');
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System.import('https://example.com/some-module.js');
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```
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Multiple instances of SystemJS may be created, each with their own import map and module registry:
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```js
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const { System } = require('systemjs');
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const system1 = new System.constructor();
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const system2 = new System.constructor();
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```
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### applyImportMap(loader, importMap) -> undefined
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Since no DOM is available for [import map installation](https://github.com/WICG/import-maps#installation), system-node.cjs provides the `applyImportMap` API. Note that calling applyImportMap multiple times on the same SystemJS instance will completely override the import map (not merge).
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```js
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const { System, applyImportMap } = require('systemjs');
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const path = require('path');
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const { pathToFileURL } = require('url');
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applyImportMap(System, {
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imports: {
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// File loading
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"module-a": "file:///Users/name/a.js",
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"module-b": pathToFileURL(path.join(process.cwd(), './b.js')),
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// Network loading
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"module-c": "https://example.com/c.js",
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}
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});
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System.import('module-a');
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// Separate import map for separate SystemJS instance
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const otherSystem = new System.constructor();
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applyImportMap(otherSystem, {
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imports: {
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"module-a": "file:///Users/name/other-a.js",
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}
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});
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otherSystem.import('module-a');
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```
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### setBaseUrl(loader, url) -> undefined
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By default, relative URLs will be resolved with `process.cwd()` as the base URL. If you wish to change the base URL, you may do so:
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```js
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const { System, setBaseUrl } = require('systemjs');
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const path = require('path');
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const { pathToFileURL } = require('url');
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// relative to process.cwd()
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System.resolve('./file.js');
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// Use a network URL as the base
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setBaseUrl(System, 'https://example.com/base/');
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// Use a file URL as the base
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setBaseUrl(System, 'file:///Users/name/some-dir/');
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setBaseUrl(System, pathToFileURL(path.join(process.cwd(), 'some-dir')) + path.sep);
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``` |