Jquery + Ajax If-Modified-Since

link.md

https://translate.google.co.uk/translate?hl=en&sl=ja&u=http://d.hatena.ne.jp/hasegawayosuke/20090925/p1&prev=search

https://translate.google.co.uk/translate?hl=en&sl=ja&u=http://blog.suusuke.info/2011/09/23/jquery%25E3%2581%25A7xhr%25E3%2582%2592%25E9%2580%2581%25E4%25BF%25A1%25E3%2581%2599%25E3%2582%258B%25E3%2581%25A8%25E3%2581%258D%25E3%2581%25AE%25E8%25A6%259A%25E6%259B%25B8/&prev=search

http://alphahydrae.com/2013/03/conditional-get-with-rails/

when we have an ajax request in jquery with cache set to false, it appends a timestamp as a param to the end of the url

e.g.

$ .ajax ({
     url: "http://example.com/",
     cache: false,
     data: {
         a: "abcd"
     },
     ...
 });

http://example.com/?a=abcd& _ = 1253861397368

if you set cache to be true, it will remove the timestamp:

$ .ajax ({
     url: "http://example.com/",
     cache: true, // URL at the end of the time stamp is not needed
     param: {
         a: "abcd"
     },
     beforeSend: function (xhr) {
         xhr.setRequestHeader ( "If-Modified-Since ", "Thu, 01 Jun 1970 00:00:00 GMT");
     },
     ...
 });

$.ajax( {
    type : 'GET',
    url : 'list.php',
    dataType: 'json',
    data : {
        pref : $('#pref').val(),
        type : $('#type').val()
    },
    beforeSend : function( xhr ){
        xhr.setRequestHeader("If-Modified-Since", "Thu, 01 Jun 1970 00:00:00 GMT");
    },
    success : function(data) {
        $('#list').empty();
        options = new Array();

        $.each(data, function(i, v){
            options.push('<option value="' + i + '">' + v + '</option>');
        });
        $('#list').append(options.join());
    },
    error : function(msg) {
       ....
    },
    complete : function(msg) {
       ....
    }
});