仅在选项标签不存在时填充选择

Question

我希望仅在尚未完成选择#current_location时填充。

$(document).ready(function(){
            $('#current_location').on('change', function (){
                   /*
                    * Populate the select
                    * I want to populate the select only if it hasn't been done yet
                    */
                   $.getJSON('fetch.php', {action: 'homepage' , key: 'current_location' }, function(data){
                       var options = '';
                       for (var x = 0; x < data.length; x++) {
                           options += '<option value="' + data[x] + '">' + data[x] + '</option>';
                       }
                       $('#current_location').html(options);
                   });


                $.getJSON('fetch.php', {action: 'homepage' , key: $('#current_location').val() }, function(data){
                    var options = '';
                    for (var x = 0; x < data.length; x++) {
                        options += '<option value="' + data[x] + '">' + data[x] + '</option>';
                    }
                    $('#destination').html(options);
                });

            });
        });

Answer 1

检查是否存在option并相应地添加option。

if($('#current_location').find('option').length < 1) {
    .... // add options
}

Answer 2

检查option长度。

var length = $('#YourSelectList')
    .children('option')
    .length;
if (length > 0) {

} else {

}