类:vm.Module
添加于:v13.0.0、v12.16.0
Stability: 1 - 实验性
此函数仅在启用--experimental-vm-modules
命令标志时可用。
vm.Module
类为在 VM 上下文中使用 ECMAScript 模块提供了一个低级接口。它是 vm.Script
类的对应物,与 ECMAScript 规范中定义的 Module Record 非常相似。
然而,与 vm.Script
不同的是,每个 vm.Module
对象从创建时就绑定到上下文。 vm.Module
对象上的操作本质上是异步的,与 vm.Script
对象的同步性质相反。使用'async' 函数可以帮助操作vm.Module
对象。
使用vm.Module
对象需要三个不同的步骤:创建/解析、链接和评估。这三个步骤在以下示例中进行了说明。
此实现位于比 ECMAScript Module loader 更低的级别。尽管计划提供支持,但目前还无法与 Loader 交互。
import vm from 'node:vm';
const contextifiedObject = vm.createContext({
secret: 42,
print: console.log,
});
// Step 1
//
// Create a Module by constructing a new `vm.SourceTextModule` object. This
// parses the provided source text, throwing a `SyntaxError` if anything goes
// wrong. By default, a Module is created in the top context. But here, we
// specify `contextifiedObject` as the context this Module belongs to.
//
// Here, we attempt to obtain the default export from the module "foo", and
// put it into local binding "secret".
const bar = new vm.SourceTextModule(`
import s from 'foo';
s;
print(s);
`, { context: contextifiedObject });
// Step 2
//
// "Link" the imported dependencies of this Module to it.
//
// The provided linking callback (the "linker") accepts two arguments: the
// parent module (`bar` in this case) and the string that is the specifier of
// the imported module. The callback is expected to return a Module that
// corresponds to the provided specifier, with certain requirements documented
// in `module.link()`.
//
// If linking has not started for the returned Module, the same linker
// callback will be called on the returned Module.
//
// Even top-level Modules without dependencies must be explicitly linked. The
// callback provided would never be called, however.
//
// The link() method returns a Promise that will be resolved when all the
// Promises returned by the linker resolve.
//
// Note: This is a contrived example in that the linker function creates a new
// "foo" module every time it is called. In a full-fledged module system, a
// cache would probably be used to avoid duplicated modules.
async function linker(specifier, referencingModule) {
if (specifier === 'foo') {
return new vm.SourceTextModule(`
// The "secret" variable refers to the global variable we added to
// "contextifiedObject" when creating the context.
export default secret;
`, { context: referencingModule.context });
// Using `contextifiedObject` instead of `referencingModule.context`
// here would work as well.
}
throw new Error(`Unable to resolve dependency: ${specifier}`);
}
await bar.link(linker);
// Step 3
//
// Evaluate the Module. The evaluate() method returns a promise which will
// resolve after the module has finished evaluating.
// Prints 42.
await bar.evaluate();
const vm = require('node:vm');
const contextifiedObject = vm.createContext({
secret: 42,
print: console.log,
});
(async () => {
// Step 1
//
// Create a Module by constructing a new `vm.SourceTextModule` object. This
// parses the provided source text, throwing a `SyntaxError` if anything goes
// wrong. By default, a Module is created in the top context. But here, we
// specify `contextifiedObject` as the context this Module belongs to.
//
// Here, we attempt to obtain the default export from the module "foo", and
// put it into local binding "secret".
const bar = new vm.SourceTextModule(`
import s from 'foo';
s;
print(s);
`, { context: contextifiedObject });
// Step 2
//
// "Link" the imported dependencies of this Module to it.
//
// The provided linking callback (the "linker") accepts two arguments: the
// parent module (`bar` in this case) and the string that is the specifier of
// the imported module. The callback is expected to return a Module that
// corresponds to the provided specifier, with certain requirements documented
// in `module.link()`.
//
// If linking has not started for the returned Module, the same linker
// callback will be called on the returned Module.
//
// Even top-level Modules without dependencies must be explicitly linked. The
// callback provided would never be called, however.
//
// The link() method returns a Promise that will be resolved when all the
// Promises returned by the linker resolve.
//
// Note: This is a contrived example in that the linker function creates a new
// "foo" module every time it is called. In a full-fledged module system, a
// cache would probably be used to avoid duplicated modules.
async function linker(specifier, referencingModule) {
if (specifier === 'foo') {
return new vm.SourceTextModule(`
// The "secret" variable refers to the global variable we added to
// "contextifiedObject" when creating the context.
export default secret;
`, { context: referencingModule.context });
// Using `contextifiedObject` instead of `referencingModule.context`
// here would work as well.
}
throw new Error(`Unable to resolve dependency: ${specifier}`);
}
await bar.link(linker);
// Step 3
//
// Evaluate the Module. The evaluate() method returns a promise which will
// resolve after the module has finished evaluating.
// Prints 42.
await bar.evaluate();
})();
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注:本文由纯净天空筛选整理自nodejs.org大神的英文原创作品 vm.Module。非经特殊声明,原始代码版权归原作者所有,本译文未经允许或授权,请勿转载或复制。