import.meta
object exposes context-specific metadata to a JavaScript module. It contains information about the module, like the module's URL.
import.meta
The syntax consists of the keyword
import
, a dot, and the identifier
meta
. Normally the left-hand side of the dot is the object on which property access is performed, but here
import
is not really an object.
import.meta
object is created by the ECMAScript implementation, with a
null
prototype. The object is extensible, and its properties are writable, configurable, and enumerable.
Given a module
my-module.js
<script type="module" src="my-module.js"></script>
you can access meta information about the module using the
import.meta
对象。
console.log(import.meta); // { url: "file:///home/user/my-module.js" }
It returns an object with a
url
property indicating the base URL of the module. This will either be the URL from which the script was obtained, for external scripts, or the document base URL of the containing document, for inline scripts.
Note that this will include query parameters and/or hash (i.e., following the
?
or
#
).
For example, with the following HTML:
<script type="module"> import './index.mjs?someURLInfo=5'; </script>
..the following JavaScript file will log the `
someURLInfo
parameter:
// index.mjs
new URL(import.meta.url).searchParams.get('someURLInfo'); // 5
The same applies when a file imports another:
// index.mjs
import './index2.mjs?someURLInfo=5';
// index2.mjs
new URL(import.meta.url).searchParams.get('someURLInfo'); // 5
Note that while Node.js will pass on query parameters (or the hash) as in the latter example, as of Node 14.1.0, a URL with query parameters will err when loading in the form
node --experimental-modules index.mjs?someURLInfo=5
(it is treated as a file rather than a URL in this context).
Such file-specific argument passing may be complementary to that used in the application-wide
location.href
(with query strings or hash added after the HTML file path) (or on Node.js, through
process.argv
).
| 规范 |
|---|
import.meta
proposal
|
|
HTML 实时标准
The definition of 'import.meta' in that specification. |
| Desktop | Mobile | Server | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
import.meta
|
Chrome 64 | Edge 79 | Firefox 62 | IE 不支持 No | Opera 51 | Safari 11.1 | WebView Android 64 | Chrome Android 64 | Firefox Android 62 | Opera Android 47 | Safari iOS 12 | Samsung Internet Android 9.0 | nodejs 10.4.0 |
完整支持
不支持
The following table provides a daily implementation status for this feature, because this feature has not yet reached cross-browser stability. The data is generated by running the relevant feature tests in Test262 , the standard test suite of JavaScript, in the nightly build, or latest release of each browser's JavaScript engine.