选择另一个div中的每个div并使用jQuery检查它的类

Question

I have a chat system and I'm showing the messages using jQuery + JSON + PHP. My problem is: I have to select each div inside the div "#chatMessages", that contains the messages, and check it's class to see if it exists, my Ajax code:

    var data = {};
$.ajax({
    type: "GET",
    dataType: "json",
    url: "../room/a.php",
    async: true,
    cache: false,
    data: data,
    success: function(response) {
        if(response.error) {
            alert(response.msg);
        } else {
            for(var i = 0; i < response.length; i ++) {
                if($("#chatScreen > *").hasClass("message" + i) == false)
                $("#chatScreen").append($("<div>",{
                    class : 'message' + response[i][1],
                    html  : response[i][0] + ' ' + response[i][4]
                }));
            }
        }
    },
    error: function (response) {

        },
    complete: function () {

        }
    });

response[i][0] contains the name, and the response[i][4] contains the message. It's working fine, but I load this function every 3000ms, so it repeat every message, how can I check div per div searching for the class 'message' + response[i][1] (that contains the unique ID from MySQL)?

I tried to use ".hasClass()" but it doesn't work.

Answer 1

If you want to know if there's any element in the DIV with a given class, you can do:

if ($("#chatScreen").find(".message"+response[i][1]).length > 0) {

You can refactor it so you don't have to search for #chatScreen every time through the loop:

var chatScreen = $("#chatScreen");
for(var i = 0; i < response.length; i ++) {
    if(chatScreen.find(".message"+response[i][1]).length > 0) {
        chatScreen.append($("<div>",{
            class : 'message' + response[i][1],
            html  : response[i][0] + ' ' + response[i][4]
        }));
    }
}