text: 
  var num1 = 9
  var fun1 = function() {
    console.log('fun1')
  }
  export {num1, fun1}
  export {num1 as number1}
  
  export var num2 = 99
  export function fun2() {
    console.log('fun2')
  }
  
  //default 只能用一次
  export default {
    num3: 999,
    fun3() {
      console.log('fun3');
    }
  }
  // var num3 = 999;
  // export {num3 as default}
  
  console.log('just log');
  