<script>
                // 变量的初始化
                // let age = 18
                // 1.变量的更新
                // age = 19
                // document.write(age)
                // 2.声明多个变量
                // let num = 20
                // let uname = '沈云兵'
                let num = 20, uname = '沈云兵', age = 18
                console.log(num)
                console.log(uname)
                console.log(age)    
            </script>