手写--实现日期格式化和实现数组乱序输出

function formatDate(dateInput, format){
    var day = dateInput.getDate() 
    var month = dateInput.getMonth() + 1  
    var year = dateInput.getFullYear()   
    format = format.replace(/yyyy/, year)
    format = format.replace(/MM/,month)
    format = format.replace(/dd/,day)
    return format
}
function randomArrayOutput(ary, fn = console.log) {
  for(let i = 0; i < ary.length; i++) {
    let randomIndex = Math.random() * ary.length - 1 - i + i
    ;[ary[i], ary[randomIndex]] = [ary[randomIndex], ary[i]]
  }
  fn(ary)
}