SharePoint Get Specific Folder List Items

You can also check whether item is folder or list item using "FileSystemObjectType"

var context = SP.ClientContext.get_current();
var web = context.get_web();

//doc is a document library server relative url
var folder = web.getFolderByServerRelativeUrl("Documents/Wildlife");

//var parentFolder = folder.get_parentFolder();
//context.load(parentFolder);

context.load(folder);
context. executeQueryAsync(function(){

 var query = new SP.CamlQuery();
 query.set_folderServerRelativeUrl(folder.get_serverRelativeUrl());
 var allItems = list.getItems(query);
 context.load(allItems, "Include(Title, FileSystemObjectType, File)");

 context.executeQueryAsync(function(){
  debugger;
  var itemsEnumerator = allItems.getEnumerator();
  while(itemsEnumerator.moveNext()){
  var item = itemsEnumerator.get_current();
  var fileType = item.get_fileSystemObjectType();
   //get the detailed information
 
    var title = item.get_item("Title")

  }
 }, function(sender, args){debugger;});

}, function(sender, args){debugger;});