Import Map Utility

Generic ImportMap class utility for the manipulation and resolution of import maps, used by JSPM.

Getting Started

$3

Node.js:
``
npm install @jspm/import-map
`

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@jspm/import-map only ships as an ES module.

example.mjs
`js
import { ImportMap } from '@jspm/import-map';

const mapUrl = import.meta.url;

const map = new ImportMap({
mapUrl, // optional
map: {
imports: {
react: 'https://cdn.com/react.js'
},
scopes: {
'https://site.com/': {
react: 'https://cdn.com/react2.js'
}
},
integrity: {
'https://cdn.com/react.js': 'sha384-...'
}
}
});

// Use the map resolver
map.resolve('react') === 'https://cdn.com/react.js';
map.resolve('react', 'https://site.com/') === 'https://cdn.com/react2.js';

// Supports normal URL resolution behaving a browser-compatible ES module resolver
map.resolve('./hello.js', 'https://site.com/') === 'https://site.com/hello.js';

// Mutate the map
map.set('react', './custom-react.js');
map.resolve('react') === new URL('./custom-react.js', mapUrl).href;

// Mutate the map inside a custom scope
map.set('react', './custom-react2.js', 'https://another.com/');
map.resolve('react', 'https://another.com/') === new URL('./custom-react2.js', mapUrl).href;

// Get the map JSON
console.log(JSON.stringify(map.toJSON(), null, 2));
// {
// "imports": {
// "react": "./custom-react.js"
// },
// "scopes": {
// "https://site.com/": {
// "react": "https://cdn.com/react2.js"
// },
// "https://another.com/": {
// "react": "./custom-react2.js"
// }
// },
// "integrity": {
// "https://cdn.com/react.js": "sha384-..."
// }
// }

// Rebase the map
map.rebase('./map/');
console.log(JSON.stringify(map.toJSON(), null, 2));
// {
// "imports": {
// "react": "../custom-react.js"
// },
// "scopes": {
// "https://site.com/": {
// "react": "https://cdn.com/react2.js"
// },
// "https://another.com/": {
// "react": "../custom-react2.js"
// }
// },
// "integrity": {
// "https://cdn.com/react.js": "sha384-..."
// }
// }

// Flatten the import map (removes unnecessary scope redundancy)
map.set('react', '../custom-react.js', 'https://site.com/');
map.flatten();
console.log(JSON.stringify(map.toJSON(), null, 2));
// {
// "imports": {
// "react": "../custom-react.js"
// },
// "scopes": {
// "https://another.com/": {
// "react": "../custom-react2.js"
// }
// },
// "integrity": {
// "https://cdn.com/react.js": "sha384-..."
// }
// }

// Replace URLs in the map
map.replace('https://cdn.com/', 'https://cdn-mirror.com/');
map.replace('https://another.com/', 'https://another-site.com/');
console.log(JSON.stringify(map.toJSON(), null, 2));
// {
// "imports": {
// "react": "../custom-react.js"
// },
// "scopes": {
// "https://another-site.com/": {
// "react": "../custom-react2.js"
// }
// },
// "integrity": {
// "https://another.com/react.js": "sha384-..."
// }
// }

// Combine subpaths in the map
// This is only supported for scopes and not top-level imports,
// to avoid losing dependency information from imports.
// (all non-returning methods support chaining)
console.log(new ImportMap({
map: {
scopes: {
"/": {
"pkg/a.js": "/pkg/a.js",
"pkg/b.js": "/pkg/b.js"
}
}
}
}).combineSubpaths().toJSON());
// {
// "imports": {},
// "scopes": {
// "/": {
// "pkg/": "/pkg/"
// }
// }
// }
``

API

See src/map.ts.

Support is also provided for conditional maps supporting a way to manage generic maps for multiple environment targets, before serializing or resolving for exact environment targets.

$3

MIT