JS 获取系统时间

yyyy-MM-dd hh:mm:ss => 2017-06-29 9:20:43

function getNowFormatDate() {
  let date = new Date()
  let seperator1 = '-'
  let seperator2 = ':'
  let month = date.getMonth() + 1
  let strDate = date.getDate()
  let minute = date.getMinutes()
  let second = date.getSeconds()
  if (month >= 1 && month <= 9) {
    month = '0' + month
  }
  if (strDate >= 0 && strDate <= 9) {
    strDate = '0' + strDate
  }
  if (minute >= 0 && minute <= 9) {
    minute = '0' + minute
  }
  if (second >= 0 && second <= 9) {
    second = '0' + second
  }
  let currentdate = date.getFullYear() + seperator1 + month + seperator1 + strDate +
    ' ' + date.getHours() + seperator2 + minute +
    seperator2 + second
  return currentdate
}

setInterval(() => {
  console.log(getNowFormatDate())
}, 1000)

or

let current_datetime = new Date()
let formatted_date = current_datetime.getFullYear() + "-" + (current_datetime.getMonth() + 1) + "-" + current_datetime.getDate() + " " + current_datetime.getHours() + ":" + current_datetime.getMinutes() + ":" + current_datetime.getSeconds() 
console.log(formatted_date) // 2020-5-26 9:51:16