nestingEnv.js

GlobalEnvironment = {
  EnvironmentRecord: { 
    // built-in identifiers
    Array: '<func>',
    Object: '<func>',
    // etc..
    
    // custom identifiers
    x: 10
  },
  outer: null
};
 
fooEnvironment = {
  EnvironmentRecord: {
    y: 20,
    bar: '<func>'
  }
  outer: GlobalEnvironment
};

barEnvironment = {
  EnvironmentRecord: {
    z: 15
  }
  outer: fooEnvironment
};