# esm-import-transformer

> Perform transformations on ESM import syntax (using import maps or to a dynamic import).

Latest version **3.0.5** (published 2025-08-08) · MIT license · 0 weekly downloads

## Install

```sh
npm install esm-import-transformer
pnpm add esm-import-transformer
yarn add esm-import-transformer
bun add esm-import-transformer
```

## Health

**Score 30/100 (F)** — status: maintenance-mode.

Positive: esm support; no vulnerabilities.

Warnings: low downloads; no types.

Negative: stale; low maintenance score.

## Facts

| | |
|---|---|
| Version | 3.0.5 |
| Published | 2025-08-08 |
| First published | 2022-06-03 |
| Weekly downloads | 0 |
| License | MIT |
| TypeScript types | none |
| Module format | ESM + CommonJS |
| Dependencies | 1 |
| Unpacked size | 10.2 KB |
| Known vulnerabilities | 0 |
| Install scripts | no |
| GitHub stars | 24 |
| Author | Zach Leatherman |
| Maintainers | zachleat |

## Links

- npm: https://www.npmjs.com/package/esm-import-transformer
- Repository: https://github.com/zachleat/esm-import-transformer
- Homepage: https://github.com/zachleat/esm-import-transformer#readme
- Issues: https://github.com/zachleat/esm-import-transformer/issues
- npm.io page: https://npm.io/package/esm-import-transformer

## Dependencies (1)

- [acorn](https://npm.io/package/acorn.md) ^8.15.0

## Recent versions

- 3.0.5 (latest) — 2025-08-08
- 3.0.4 — 2025-08-06
- 3.0.3 — 2025-04-17
- 3.0.2 — 2023-12-14
- 3.0.1 — 2023-12-14
- 3.0.0 — 2023-11-03
- 2.0.0 — 2023-11-03
- 1.0.1 — 2022-06-03
- 1.0.0 — 2022-06-03

## README

# 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");
```

### Transform with an import map

Pass in a source code string and an [import maps](https://github.com/WICG/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";`
```

### Transform to dynamic `import()`

```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");`
```

### Transform to `require()`

_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");`
```

### Has imports?

_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](https://www.npmjs.com/package/esm-import-transformer)

```
npm install esm-import-transformer
```

---
_Source: https://npm.io/package/esm-import-transformer · Machine-readable twin of the npm.io package page. Health data is recomputed on every publish._