自定义评估函数

¥Custom evaluation functions

当新建 repl.REPLServer 时，可能会提供自定义评价函数。例如，这可用于实现完全定制的 REPL 应用。

¥When a new repl.REPLServer is created, a custom evaluation function may be provided. This can be used, for instance, to implement fully customized REPL applications.

执行函数接受以下四个参数：

¥An evaluation function accepts the following four arguments:

• code <string> 要执行的代码（例如 1 + 1）。

  ¥code <string> The code to be executed (e.g. 1 + 1).

• context <Object> 执行代码的上下文。这可以是 JavaScript global 上下文，也可以是特定于 REPL 实例的上下文，具体取决于 useGlobal 选项。

  ¥context <Object> The context in which the code is executed. This can either be the JavaScript global context or a context specific to the REPL instance, depending on the useGlobal option.

• replResourceName <string> 与当前代码执行关联的 REPL 资源的标识符。这对于调试目的很有用。

  ¥replResourceName <string> An identifier for the REPL resource associated with the current code evaluation. This can be useful for debugging purposes.

• callback <Function> 代码执行完成后调用的函数。回调函数接受两个参数：

  ¥callback <Function> A function to invoke once the code evaluation is complete. The callback takes two parameters:

  • 执行过程中发生错误时提供的错误对象；未发生错误时提供 null/undefined。

    ¥An error object to provide if an error occurred during evaluation, or null/undefined if no error occurred.

  • 代码评估的结果（如果提供错误，则此结果无关）。

    ¥The result of the code evaluation (this is not relevant if an error is provided).

以下示例展示了一个 REPL，它对给定数字进行平方，如果提供的输入实际上不是数字，则会打印错误：

¥The following illustrates an example of a REPL that squares a given number, an error is instead printed if the provided input is not actually a number:

import repl from 'node:repl';

function byThePowerOfTwo(number) {
  return number * number;
}

function myEval(code, context, replResourceName, callback) {
  if (isNaN(code)) {
    callback(new Error(`${code.trim()} is not a number`));
  } else {
    callback(null, byThePowerOfTwo(code));
  }
}

repl.start({ prompt: 'Enter a number: ', eval: myEval });const repl = require('node:repl');

function byThePowerOfTwo(number) {
  return number * number;
}

function myEval(code, context, replResourceName, callback) {
  if (isNaN(code)) {
    callback(new Error(`${code.trim()} is not a number`));
  } else {
    callback(null, byThePowerOfTwo(code));
  }
}

repl.start({ prompt: 'Enter a number: ', eval: myEval });拷贝