jQuery .on("keyup")仅在ajax调用后触发一次，如果值发生更改则不会更新，并使用它来使用邮政编码更新城市和州

$("#zipcode").on("keyup", function() {
    // 在这里编写相应的代码
});

$("#zipcode").on("keyup", function() {
    var zipcode = $(this).val();
    
    // 发送AJAX请求
    $.ajax({
        url: "https://example.com/getCityAndState",
        method: "POST",
        data: { zipcode: zipcode },
        success: function(response) {
            // 在这里处理服务器返回的数据
        }
    });
});

$("#zipcode").on("keyup", function() {
    var zipcode = $(this).val();
    
    $.ajax({
        url: "https://example.com/getCityAndState",
        method: "POST",
        data: { zipcode: zipcode },
        success: function(response) {
            // 更新城市和州信息
            $("#city").text(response.city);
            $("#state").text(response.state);
        }
    });
});

var lastZipcode = "";

$("#zipcode").on("keyup", function() {
    var zipcode = $(this).val();
    
    if (zipcode !== lastZipcode) {
        lastZipcode = zipcode;
        
        $.ajax({
            url: "https://example.com/getCityAndState",
            method: "POST",
            data: { zipcode: zipcode },
            success: function(response) {
                // 更新城市和州信息
                $("#city").text(response.city);
                $("#state").text(response.state);
            }
        });
    }
});