globalPreload()

加载程序 API 正在重新设计。这个钩子可能会消失或者它的签名可能会改变。不要依赖下面描述的 API。

¥The loaders API is being redesigned. This hook may disappear or its signature may change. Do not rely on the API described below.

在此 API 的先前版本中，此钩子名为 getGlobalPreloadCode。

¥In a previous version of this API, this hook was named getGlobalPreloadCode.

• context <Object> 辅助预加载代码的信息

  ¥context <Object> Information to assist the preload code

  • port <MessagePort>

• 返回：<string> 应用启动前运行的代码

  ¥Returns: <string> Code to run before application startup

有时可能需要在应用运行所在的同一全局作用域内运行一些代码。此钩子允许返回在启动时作为宽松模式脚本运行的字符串。

¥Sometimes it might be necessary to run some code inside of the same global scope that the application runs in. This hook allows the return of a string that is run as a sloppy-mode script on startup.

类似于 CommonJS 封装器的工作方式，代码在隐式函数范围内运行。唯一的参数是一个类似 require 的函数，可用于加载像 "fs" 这样的内置函数：getBuiltin(request: string)。

¥Similar to how CommonJS wrappers work, the code runs in an implicit function scope. The only argument is a require-like function that can be used to load builtins like "fs": getBuiltin(request: string).

如果代码需要更高级的 require 功能，则必须使用 module.createRequire() 构造自己的 require。

¥If the code needs more advanced require features, it has to construct its own require using module.createRequire().

export function globalPreload(context) {
  return `\
globalThis.someInjectedProperty = 42;
console.log('I just set some globals!');

const { createRequire } = getBuiltin('module');
const { cwd } = getBuiltin('process');

const require = createRequire(cwd() + '/<preload>');
// [...]
`;
} 拷贝

为了允许应用和加载器之间的通信，向预加载代码提供了另一个参数：port。这可以作为加载器钩子的参数和钩子返回的源文本内部。必须注意正确调用 port.ref() 和 port.unref() 以防止进程处于无法正常关闭的状态。

¥In order to allow communication between the application and the loader, another argument is provided to the preload code: port. This is available as a parameter to the loader hook and inside of the source text returned by the hook. Some care must be taken in order to properly call port.ref() and port.unref() to prevent a process from being in a state where it won't close normally.

/**

 * This example has the application context send a message to the loader

 * and sends the message back to the application context
 */
export function globalPreload({ port }) {
  port.onmessage = (evt) => {
    port.postMessage(evt.data);
  };
  return `\
    port.postMessage('console.log("I went to the Loader and back");');
    port.onmessage = (evt) => {
      eval(evt.data);
    };
  `;
} 拷贝