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import.meta

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since enero de 2020.

El objeto import.meta expone el contenido especifico de la metadata al módulo JavaScript. Este contiene informacion sobre el módulo, como por ejemplo, la URL del mismo.

In this article

Syntax

import.meta

Descripción

La sintasis consiste de la palabra clave import,un punto, y un identificador meta. Normalmente, la parte a la izquierda del punto es el objeto sobre el cual la accion es realizada, pero aqui import no es realmente un objeto.

El objeto import.meta es creado por la implementacion ECMAScript , con un prototipo null . El objeto es extensible y sus propiedades son grabables, editables y enumerables.

Ejemplos

Usando import.meta

Dado un módulo my-module.js

html
<script type="module" src="my-module.js"></script>

puedes acceder a la meta información sobre el módulo usando el objeto import.meta.

js
console.log(import.meta); // { url: "file:///home/user/my-module.js" }

Este retorna un objeto con una propiedad url indicando la URL base del módulo.Esta será la URL de la que el script fue obtenido, por scripts externos, o la URL base del documento que contiene el documento, por scripts inline.

Nota que este incluirá parametros de la consulta y/o el hash (ej: seguido del ? or #).

Por ejemplo, con el siguiente HTML:

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

..El siguiente archivo JavaScript registrará el parámetro someURLInfo:

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

Lo mismo aplica cuando un archivo importa otro:

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

Nota que mientras Node.js pasa en la consulta los parámetros (o el hash ) como en el último ejemplo, a partir de Node 14.1.0, una URL con parametros en la consulta fallará cuando se carguen en el formato node --experimental-modules index.mjs?someURLInfo=5 (es tratado como un archivo en lugar de una URL en este contexto).

Tal argumento específico del archivo podria ser complementario al usado en toda la aplicacion location.href (con consultas strings o hash añadidas despues de la ruta HTML) (o en Node.js, mediante process.argv).

Especificaciones

Specification
ECMAScript® 2027 Language Specification
# prod-ImportMeta

Browser compatibility

Enable JavaScript to view this browser compatibility table.

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      1. import.meta.resolve()
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  14. Misc
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    5. Strict mode
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