vm.runInThisContext(code[, options])


  • code <string> 将被编译和运行的 JavaScript 代码。
  • options <Object> | <string>
    • filename <string> 定义供脚本生成的堆栈跟踪信息所使用的文件名。默认值: 'evalmachine.<anonymous>'
    • lineOffset <number> 定义脚本生成的堆栈跟踪信息所显示的行号偏移。默认值: 0
    • columnOffset <number> 定义脚本生成的堆栈跟踪信息所显示的列号偏移。默认值: 0
    • displayErrors <boolean> 当值为 true 的时候,假如在解析代码的时候发生错误 Error,引起错误的行将会被加入堆栈跟踪信息。默认值: true
    • timeout <integer> 定义在被终止执行之前此 code 被允许执行的最大毫秒数。假如执行被终止,将会抛出一个错误 Error。该值必须是严格正整数。
    • breakOnSigint <boolean> 若值为 true,接收到 SIGINTCtrl+C)会终止执行并抛出 Error。 通过 process.on('SIGINT') 方法所设置的消息响应机制在代码被执行时会被屏蔽,但代码被终止后会被恢复。 默认值: false
    • cachedData <Buffer> | <TypedArray> | <DataView> 为源码提供一个可选的存有 V8 代码缓存数据的 BufferTypedArrayTypedArray。 如果提供了,则 cachedDataRejected 的值将会被设为要么为 true 要么为 false,这取决于 v8 引擎对数据的接受状况。
    • produceCachedData <boolean> 当值为 truecachedData 不存在的时候,V8 将会试图为 code 生成代码缓存数据。 一旦成功,则一个有 V8 代码缓存数据的 Buffer 将会被生成和储存在返回的 vm.Script 实例的 cachedData 属性里。 cachedDataProduced 的值会被设置为 true 或者 false,这取决于代码缓存数据是否被成功生成。 不推荐使用此选项,而应该使用 script.createCachedData()默认值: false
    • importModuleDynamically <Function> 在调用 import() 时评估此模块期间调用。 如果未指定此选项,则对 import() 的调用将拒绝 ERR_VM_DYNAMIC_IMPORT_CALLBACK_MISSING。 此选项是实验的模块的 API 的一部分,不应被视为稳定。
  • 返回: <any> 脚本中执行的最后一个语句的结果。

vm.runInThisContext() 在当前的 global 对象的上下文中编译并执行 code,最后返回结果。 运行中的代码无法获取本地作用域,但可以获取当前的 global 对象。

如果 options 是字符串,则它指定文件名。

下面的例子演示了使用 vm.runInThisContext() 和 JavaScript 的 eval() 方法去执行相同的一段代码:

const vm = require('vm');
let localVar = 'initial value';

const vmResult = vm.runInThisContext('localVar = "vm";');
console.log(`vmResult: '${vmResult}', localVar: '${localVar}'`);
// 打印: vmResult: 'vm', localVar: 'initial value'

const evalResult = eval('localVar = "eval";');
console.log(`evalResult: '${evalResult}', localVar: '${localVar}'`);
// 打印: evalResult: 'eval', localVar: 'eval'

正因 vm.runInThisContext() 无法获取本地作用域,故 localVar 的值不变。 相反,eval() 确实能获取本地作用域,所以 localVar 的值被改变了。 如此看来, vm.runInThisContext() 更像是间接的执行 eval(), 就像 (0,eval)('code')

  • code <string> The JavaScript code to compile and run.
  • options <Object> | <string>
    • filename <string> Specifies the filename used in stack traces produced by this script. Default: 'evalmachine.<anonymous>'.
    • lineOffset <number> Specifies the line number offset that is displayed in stack traces produced by this script. Default: 0.
    • columnOffset <number> Specifies the column number offset that is displayed in stack traces produced by this script. Default: 0.
    • displayErrors <boolean> When true, if an Error occurs while compiling the code, the line of code causing the error is attached to the stack trace. Default: true.
    • timeout <integer> Specifies the number of milliseconds to execute code before terminating execution. If execution is terminated, an Error will be thrown. This value must be a strictly positive integer.
    • breakOnSigint <boolean> If true, receiving SIGINT (Ctrl+C) will terminate execution and throw an Error. Existing handlers for the event that have been attached via process.on('SIGINT') are disabled during script execution, but continue to work after that. Default: false.
    • cachedData <Buffer> | <TypedArray> | <DataView> Provides an optional Buffer or TypedArray, or DataView with V8's code cache data for the supplied source. When supplied, the cachedDataRejected value will be set to either true or false depending on acceptance of the data by V8.
    • produceCachedData <boolean> When true and no cachedData is present, V8 will attempt to produce code cache data for code. Upon success, a Buffer with V8's code cache data will be produced and stored in the cachedData property of the returned vm.Script instance. The cachedDataProduced value will be set to either true or false depending on whether code cache data is produced successfully. This option is deprecated in favor of script.createCachedData(). Default: false.
    • importModuleDynamically <Function> Called during evaluation of this module when import() is called. If this option is not specified, calls to import() will reject with ERR_VM_DYNAMIC_IMPORT_CALLBACK_MISSING. This option is part of the experimental modules API. We do not recommend using it in a production environment.
  • Returns: <any> the result of the very last statement executed in the script.

vm.runInThisContext() compiles code, runs it within the context of the current global and returns the result. Running code does not have access to local scope, but does have access to the current global object.

If options is a string, then it specifies the filename.

The following example illustrates using both vm.runInThisContext() and the JavaScript eval() function to run the same code:

const vm = require('vm');
let localVar = 'initial value';

const vmResult = vm.runInThisContext('localVar = "vm";');
console.log(`vmResult: '${vmResult}', localVar: '${localVar}'`);
// Prints: vmResult: 'vm', localVar: 'initial value'

const evalResult = eval('localVar = "eval";');
console.log(`evalResult: '${evalResult}', localVar: '${localVar}'`);
// Prints: evalResult: 'eval', localVar: 'eval'

Because vm.runInThisContext() does not have access to the local scope, localVar is unchanged. In contrast, eval() does have access to the local scope, so the value localVar is changed. In this way vm.runInThisContext() is much like an indirect eval() call, e.g. (0,eval)('code').