js日期转换yyyy-MM-dd

function vertDate(obj) {
    //日期转yyyy-MM-dd
    var date = new Date(obj)
    var y = 1900 + date.getYear()
    var m = '0' + (date.getMonth() + 1)
    var d = '0' + date.getDate()
    return y + '-' + m.substring(m.length - 2, m.length) + '-' + d.substring(d.length - 2, d.length)
  }