判断是否为正确日期格式的javascript

function isdatestring(sdate)
{    var iamonthdays = [31,28,31,30,31,30,31,31,30,31,30,31]
    var iadate = new array(3)
    var year, month, day

    if (arguments.length != 1) return false
    iadate = sdate.tostring().split("-")
    if (iadate.length != 3) return false
    if (iadate[1].length > 2 || iadate[2].length > 2) return false

    year = parsefloat(iadate[0])
    month = parsefloat(iadate[1])
    day=parsefloat(iadate[2])

    if (year < 1900 || year > 2100) return false
    if (((year % 4 == 0) && (year % 100 != 0)) || (year % 400 == 0)) iamonthdays[1]=29;
    if (month < 1 || month > 12) return false
    if (day < 1 || day > iamonthdays[month – 1]) return false
    return true
}