Pass functions in a vm script context

问题

Let's say I have a library module that looks like this:

module.exports = {
    increment: function() {
         count++;
    }
}

And I'd like to use it in a dynamically generated script that looks like this:

(function() { lib.increment(); })();

by passing it in a sandbox:

var sandbox = {
    count: 1
    lib: require('./lib')
}
var script = new vm.Script('(function() { lib.increment() })();');
script.runInNewContext(sandbox);

The obvious problem I run into is that I on the one hand can't require "lib" because "count" is not defined in lib.js ; on the other hand if I define var count above the exports of the "lib.js" file, this new count variable will be affected instead of the one in the sandbox.

Here are the constraints that I would like to respect:

Use vm and not a eval() nor a require() on a generated file
Have "lib" defined in a external file
No modification of the automatically generated script, so no use of lib.increment.apply(context) or similar

The only solutions I've found so far is to prepend the lib functions in the generated script as a string, or to define them directly on the sandbox object, which I find to be a less desirable option.

There doesn't seem to be any way of passing a context of variables on the require call.

回答1:

One way of accomplishing this is have your lib module be a function that takes in a context then returns the correct interface.

lib.js

module.exports = function(context) {
  var count = context.count;
  return {
    increment: function() {
      count++;
    }
  };
};

main.js

var sandbox = {
  count: 1
};
sandbox.lib = require('./lib')(sandbox);
var script = new vm.Script('(function() { lib.increment() })();');
script.runInNewContext(sandbox);

来源：https://stackoverflow.com/questions/38316876/pass-functions-in-a-vm-script-context

标签

javascript

node.js