Question

我正在尝试实现一种在Node.js VM中运行“顺序编写”异步JS代码的方法，并获得对相应上下文对象的访问权限。我尝试使用由await转换的即将发布的ES7 babel.js功能。

在我看来，script.runInContext()在后台运行，而主循环继续，因此我无法从VM的上下文中获得结果。

我的示例代码如下：

var vm = require('vm');
var request = require('request-promise');
var babel = require("babel-core");

// VM context object
var contextCache = { 
    context: { 
        request: request 
    } 
};

// ES 7 code
var code = "var res = await request('http://www.google.de')";

// Wrap the code
code = "(async function() { " + code + " })()";

// Transpile code ES7 -> ES5
var regeneratedCode = babel.transform(code, { "ast": false, "presets": ["stage-0"] }).code

// Create VM context
var vmContext = new vm.createContext(contextCache.context);

// Create virtual script
var script = new vm.Script(regeneratedCode);

// Run script
script.runInContext(vmContext, {displayErrors: true, timeout: 30000});

// Check if variable was set -> Is undefined
console.log(contextCache.context.res);

有没有办法以同步方式从上下文评估中检索异步结果？

参考文献：

Answer 1

I found a way to get this working... Basically it's using the Apples::Apples() : Fruits("Apple", BREAKFAST), number( 5 ) { } variable for the context object inside the executed code, and calling a callback function from inside as the last operation:

this

Answer 2

const vm = require('vm');

(async () => {
  const sandbox = {
    a: 1
  };
  await new Promise(resolve => {
    sandbox.resolve = resolve;
    const code = 'Promise.resolve(2).then(result => {a = result; resolve();})';
    const script = new vm.Script(code);
    const context = new vm.createContext(sandbox);
    script.runInContext(context);
  });
  console.log(sandbox.a); // 2
})();

Gist here

Answer 3

您可以删除var ，而不用将this.替换为var。

这将使变量对于上下文是全局的，然后可以在vm外部进行访问。

如何使用ES7语法

3 个答案: