JavaScript高级__执行上下文代码案例

在栈内存中，后进先出

<script>
  console.log('gb:' + i)
  var i = 1
  foo(1)
  function foo(i) {
    if (i == 4) {
      return
    }
    console.log('fb:' + i)
    foo(i + 1)
    console.log('fe:' + i)
  }
  console.log('ge:' + i)
</script>

　　输出

 声明提升

案例1

function a() {}
var a;
console.log(typeof a)  // function

案例2

if (!(b in window)) {
  var b = 1
}
console.log(b) // undefineda

案例3

var c = 1
function c(c) {
  console.log(c)
  var c = 3
}
c(2) // 报错 Uncaught TypeError: c is not a function