Namespace node.vm

Method Detail

• static node.vm.createContext()
• static node.vm.createScript(code, ctx, name)
  createScript compiles code as if it were loaded from filename, but does not run it. Instead, it returns a vm.Script object representing this compiled code. This script can be run later many times using methods below. The returned script is not bound to any global object. It is bound before each run, just for that run. filename is optional. In case of syntax error in code, createScript prints the syntax error to stderr and throws an exception.

  Parameters:

  {string} code

  {string} ctx

  {string} name
• static node.vm.runInContext()
• static node.vm.runInNewContext()
  Similar to vm.runInNewContext a method of a precompiled Script object. script.runInNewContext runs the code of script with sandbox as the global object and returns the result. Running code does not have access to local scope. sandbox is optional. Example: compile code that increments a global variable and sets one, then execute this code multiple times. These globals are contained in the sandbox.

      var util = require('util'),
          vm = require('vm'),
          sandbox = {
            animal: 'cat',
            count: 2
          };
  
      var script = vm.createScript('count += 1; name = "kitty"', 'myfile.vm');
  
      for (var i = 0; i < 10 ; i += 1) {
        script.runInNewContext(sandbox);
      }
  
      console.log(util.inspect(sandbox));
  
      // { animal: 'cat', count: 12, name: 'kitty' }
  

  Note that running untrusted code is a tricky business requiring great care. To prevent accidental global variable leakage, script.runInNewContext is quite useful, but safely running untrusted code requires a separate process.
• static node.vm.runInThisContext()
  Similar to vm.runInThisContext but a method of a precompiled Script object. script.runInThisContext runs the code of script and returns the result. Running code does not have access to local scope, but does have access to the global object (v8: in actual context). Example of using script.runInThisContext to compile code once and run it multiple times:

      var vm = require('vm');
  
      globalVar = 0;
  
      var script = vm.createScript('globalVar += 1', 'myfile.vm');
  
      for (var i = 0; i < 1000 ; i += 1) {
        script.runInThisContext();
      }
  
      console.log(globalVar);
  
      // 1000