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    @import-maps/resolve
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    1.0.1 • Public • Published

    Resolve import-maps

    Library for parsing and resolving import maps.

    Part of Open Web Components: guides, tools and libraries for modern web development and web components

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    Usage

    npm i --save-dev @import-maps/resolve

    Base URL

    Parsing and resolving import maps requires a base URL. This is an instance of the URL constructor.

    This can be a browser URL:

    const myUrl = new URL('https://www.example.com/');

    Or a file URL when working with a file system. The pathToFileURL function is useful for converting a file path to a URL object:

    import path from 'path';
    import { pathToFileURL } from 'url';
    
    const fileUrl1 = new URL('file:///foo/bar');
    const fileUrl2 = pathToFileURL(path.join(process.cwd(), 'foo', 'bar'));

    Parsing an import map from a string

    The parseFromString function parses an import map from a JSON string. It returns the parsed import map object to be used when resolving import specifiers.

    import { parseFromString } from '@import-maps/resolve';
    
    // get the import map from somewhere, for example read it from a string
    const importMapString = '{ "imports": { "foo": "./bar.js" } }';
    // create a base URL to resolve imports relatively to
    const baseURL = new URL('https://www.example.com/');
    
    const importMap = parseFromString(importMapString, baseURL);

    Parsing an import map from an object

    If you already have an object which represents the import map, it still needs to be parsed to validate it and to prepare it for resolving. You can use the parse function for this.

    import { parse } from '@import-maps/resolve';
    
    // get the import map from somewhere, for example read it from a string
    const rawImportMap = { imports: { foo: './bar.js' } };
    // create a base URL to resolve imports relatively to
    const baseURL = new URL('https://www.example.com/');
    
    const importMap = parse(importMapString, baseURL);

    Resolving imports

    Once you've created a parsed import map, you can start resolving specifiers. The resolve function returns an object with the resolved URL as well as a boolean whether the import was matched. When a bare import is not found in the import map, resolve returns null. When a relative import isn't found, the resolved URL is returned, and matched will be set to false.

    import { resolve } from '@import-maps/resolve';
    
    const importMapString = '{ "imports": { "foo": "./bar.js" } }';
    const baseURL = new URL('https://www.example.com/');
    const importMap = parseFromString(importMapString, baseURL);
    
    const scriptUrl = new URL('https://www.example.com/my-app.js');
    
    // resolvedImport: https://www.example.com/bar.js, matched: true
    const { resolvedImport, matched } = resolve('foo', baseURL, scriptUrl);
    
    // resolvedImport: https://www.example.com/x.js, matched: false
    const { resolvedImport, matched } = resolve('./x.js', baseURL, scriptUrl);
    
    // resolvedImport: null, matched: false
    const { resolvedImport, matched } = resolve('bar', baseURL, scriptUrl);

    If you need to use the resolved path on the file system, you can use the fileURLToPath utility:

    import { fileURLToPath } from 'url';
    import { resolve } from '@import-maps/resolve';
    
    const { resolvedImport } = resolve(importMapString, baseURL, scriptUrl);
    
    // the fully resolved file path
    console.log(fileURLToPath(resolvedImport));

    Acknowledgments

    This implementation is heavily based on the import-maps reference implementation.

    Install

    npm i @import-maps/resolve

    DownloadsWeekly Downloads

    3,679

    Version

    1.0.1

    License

    MIT

    Unpacked Size

    118 kB

    Total Files

    18

    Last publish

    Collaborators

    • modern-web
    • d4kmor