esm-import-transformer

Can transform any ESM source code import URLs using an import maps object. This package works in ESM or CJS.

``js
// Input source code:
import {html, css, LitElement} from "lit";

// Transform with an import map:
import {html, css, LitElement} from "https://cdn.jsdelivr.net/gh/lit/dist@2/core/lit-core.min.js";

// Or transform to a dynamic import:
const {html, css, LitElement} = await import("lit");

// Or transform to CommonJS require:
const {html, css, LitElement} = require("lit");
`

Usage

`js
// ESM
import { ImportTransformer } from "esm-import-transformer";

// or CJS
const { ImportTransformer } = await import("esm-import-transformer");
`

$3

Pass in a source code string and an import maps object.

`js
let sourceCode = import {html, css, LitElement} from "lit";;
let it = new ImportTransformer(sourceCode);

let importMap = {
imports: {
lit: "https://cdn.jsdelivr.net/gh/lit/dist@2/core/lit-core.min.js"
}
};
let outputCode = it.transformWithImportMap(importMap);
// returns: import {html, css, LitElement} from "https://cdn.jsdelivr.net/gh/lit/dist@2/core/lit-core.min.js";
`

$3

`js
let sourceCode = import {html, css, LitElement} from "lit";;
let it = new ImportTransformer(sourceCode);

let outputCode = it.transformToDynamicImport();
// returns: const {html, css, LitElement} = await import("lit");
`

$3

_Added in v3.0.1_: This method does _not_ require that the downstream package is CommonJS, but remember that _running_ the resulting code will fail if you try to require an ESM package (in some JavaScript environments, e.g. Node < 20).

`js
let sourceCode = import {html, css, LitElement} from "lit";;
let it = new ImportTransformer(sourceCode);

let outputCode = it.transformToRequire();
// returns: const {html, css, LitElement} = require("lit");
`

$3

_Added in v3.0.2_ Returns true if the code has any top level import.

`js
let sourceCode = import {html, css, LitElement} from "lit";;
let it = new ImportTransformer(sourceCode);
it.hasImports(); // true
`

`js
let sourceCode = const {html, css, LitElement} = require("lit");;
let it = new ImportTransformer(sourceCode);
it.hasImports(); // false
`

Installation

Available on npm

`
npm install esm-import-transformer
``