年月日 手写思路

function setDate(){
    var minYear = 1900
    var maxYear = (new Date).getFullYear();
    var yearSel = $('#year');
    var monthSel =$('#month');
    var daySel = $('#days');
    console.log(maxYear);

    for(var y = maxYear;y >= minYear;y--){
        var yearOpt = $('<dd></dd>');
        yearOpt.attr({'data-value':y});
        yearOpt.text(y);
        yearSel.append(yearOpt)
    }

    yearSel.find('dd').click(function(){
        removeOption(monthSel);
        addOption(12,monthSel);
        removeOption(daySel);
    });

    monthSel.on('click','dd',function(){
        removeOption(daySel);
        var year = yearSel.closest('.seleinput').find('.input').val();
        var month = $(this).text();
        if(month==1 || month==3 || month==5 || month==7 || month==8 || month==10 || month==12){
            addOption(31,daySel)
        }else if(month==4 || month==6 || month==9 || month==11){
            addOption(30,daySel)
        }else if(month==2){
            if((year%4 == 0 && year%100 != 0 ) || (year%400 == 0)){
                addOption(29,daySel)
            }else{  
                addOption(28,daySel)
            }
        }
    });

    function addOption(num,parent){
        //parent：父对象
        //unit：单位（年/月/日）
         //num：选项个数
        for(var index=1;index <= num;index++){
            var opt =$('<dd></dd>');
            opt.attr({'data-value':index});
            if(index<10){index = '0'+index};
            opt.text(index);
            parent.append(opt);
        }
    }
    
    function removeOption(parent){
        //parent：父对象
        parent.empty();
    }


}