let a = 'Hello'

function first() {
  console.log('Inside first function')
  second()
  console.log('Again inside first function')
}

function second() {
  console.log('Inside second function')
}

first()

console.log('Inside Global execution context')

function foo(a, b) {
  var c = a + b
}

// argument object
Arguments: {0: 2, 1: 3, length: 2}

let a = 20
const b = 30
var c

function multiply(e, f) {
  var g = 20
  return e * f * g
}

c = multiply(20, 30)

GlobalExectionContext = {  // 全局上下文
  LexicalEnvironment: {  // 词法环境
    EnvironmentRecord: {  // 环境记录
      type: 'Object', // 类型
      // 标识符
      a: <uninitialized>,
      b: <uninitialized>,
      multiply: <func>
    },
    outer: <null>, // 对外部环境引用
  },
  VariableEnvironment: { // 变量环境
    EnvironmentRecord: {  // 环境记录
      type: 'Object',
      c: undefined
    },
    outer: <null>, // 对外部环境引用
  }，
  ThisBinding: <Global Object>  // this绑定
}

GlobalExectionContext = {
  LexicalEnvironment: {
    EnvironmentRecord: {
      type: 'Object',
      a: 20,
      b: 30,
      multiply: <func>
    },
    outer: <null>
  },
  VariableEnvironment: {
    EnvironmentRecord: {
      type: 'Object',
      c: undefined
    }
    outer: <null>
  },
  ThisBinding: <Global Object>
}

FunctionExectionContext = {
  LexicalEnvironment: {
    EnvironmentRecord: {
      type: 'Declarative',
      arguments: {
        0: 20,
        1: 30,
        length: 2
      }
    },
    outer: <GlobalLexicalEnvironment>
  },
  VariableEnvironment: {
    EnvironmentRecord: {
     Type: "Declarative",
     g: undefined
    },
    outer: <GlobalLexicalEnvironment>,
  }，
  thisBinding: <Global Object or undefined>
}

FunctionExectionContext = {
  LexicalEnvironment: {
    EnvironmentRecord: {
      type: 'Declarative',
      arguments: {
        0: 20,
        1: 30,
        length: 2
      }
    },
    outer: <GlobalLexicalEnvironment>
  },
  VariableEnvironment: {
    EnvironmentRecord: {
     Type: "Declarative",
     g: 20
    },
    outer: <GlobalLexicalEnvironment>,
  }，
  thisBinding: <Global Object or undefined>
}