import.meta

The import.meta object is created by the host environment, as an extensible null-prototype object where all properties are writable, configurable, and enumerable. The spec doesn't specify any properties to be defined on it, but hosts usually implement the following properties:

url

The full URL to the module, includes query parameters and/or hash (following the ? or #). In browsers, this is either the URL from which the script was obtained (for external scripts), or the URL of the containing document (for inline scripts). In Node.js, this is the file path (including the file:// protocol).

resolve

Resolves a module specifier to a URL using the current module's URL as base.

The import.meta syntax consists of the keyword import, a dot, and the identifier meta. Because import is a reserved word, not an identifier, this is not a property accessor, but a special expression syntax.

The import.meta meta-property is available in JavaScript modules; using import.meta outside of a module (including direct eval() within a module) is a syntax error.

Using query parameters in the import specifier allows module-specific argument passing, which may be complementary to reading parameters from the application-wide window.location (or on Node.js, through process.argv). For example, with the following HTML:

<script type="module">
  import "./index.mjs?someURLInfo=5";
</script>

The index.mjs module is able to retrieve the someURLInfo parameter through import.meta:

// index.mjs
new URL(import.meta.url).searchParams.get("someURLInfo"); // 5

The same applies when a module imports another:

// index.mjs
import "./index2.mjs?someURLInfo=5";

// index2.mjs
new URL(import.meta.url).searchParams.get("someURLInfo"); // 5

The ES module implementation in Node.js supports resolving module specifiers containing query parameters (or the hash), as in the latter example. However, you cannot use queries or hashes when the module is specified through the CLI command (like node index.mjs?someURLInfo=5), because the CLI entrypoint uses a more CommonJS-like resolution mode, treating the path as a file path rather than a URL. To pass parameters to the entrypoint module, use CLI arguments and read them through process.argv instead (like node index.mjs --someURLInfo=5).

In Node.js CommonJS modules, there's a __dirname variable that contains the absolute path to the folder containing current module, which is useful for resolving relative paths. However, ES modules cannot have contextual variables except for import.meta. Therefore, to get the current module's file path, you can use import.meta.url.

Before (CommonJS):

const fs = require("fs/promises");
const path = require("path");

const filePath = path.join(__dirname, "someFile.txt");
fs.readFile(filePath, "utf8").then(console.log);

After (ES modules):

import fs from "node:fs/promises";
import { fileURLToPath } from "node:url";

const filePath = fileURLToPath(new URL("./someFile.txt", import.meta.url));
fs.readFile(filePath, "utf8").then(console.log);

• import
• export