Fetching movie data using jQuery
As pointed out by Blindman67: in render(wrapper, items);, items is not defined.



const url = 'http://moviedatas.com/movies';



Const variable used only one time, you can remove it and write url: http://moviedatas.com/movies

Same for

const wrapper = $(this);

Use ES6 arrow function shortcut syntax () =&gt;


    success: function(response) {
        movieList.each(function() {
            const wrapper = $(this);

            render(wrapper, items);
        });
    },



7 lines in one, shorter is cleaner.

success: (response) =&gt; movieList.each(() =&gt; render($(this), response.items)),


error: function(error) {
    onError(movieList);
}



If you don't use error XHR response, just write

error: () =&gt; onError(movieList)

Write jsDoc docstring above functions to help developers and IDE understanding what is happening.
If functions are becoming inline, you may write them directly in caller function.


Full review (without docstring)

function loadMovies() {
   const movieList = $('.movie_list');

   // setOnLoading
   movieList.each(() =&gt; $(this).html('Loading...'));

   $.ajax({
       method: 'GET',
       url    : 'http://moviedatas.com/movies',
       data   : { count: 10 },
       success: (response) =&gt; movieList.each(() =&gt; render($(this), response.items))
       error  : () =&gt; movieList.each(() =&gt; $(this).html(''));
   });
}

function render(wrapper, items) {
   const template = `&lt;div class="movie_item"&gt;
     &lt;div class="title"&gt;{title}&lt;/div&gt;
     &lt;div class="desc"&gt;{description}&lt;/div&gt;
    &lt;/div&gt;`;

   let movies = '';

   for (let i = 0; i &lt; items.length; i++) {
       movies += template
           .replace('{title}', items[i].title)
           .replace('{description}', items[i].description);
   }

   wrapper.html(movies);
}


Also, I don't understand the logic of getting a movie list data and then iterating over a movie list HTML to put movies in. It becomes a list of list of movies...