function renderSlider(playlist){ 
  return `<div class="carousel slide" data-ride="carousel" data-interval="1000">
    <div class="carousel-inner">` +
      playlist.map((item, index) => `
        <div class="item ${index === 0? 'active' : ''}">
          <img src="${item.url}" alt="image1">
        </div>
      `) +
    `</div>
  </div>`;
}

$.getJSON('playlist.json')
  .done(function(playlist) {
    console.log(playlist);
    $('#slider').html(renderSlider(playlist));
    $('#slider .carousel').carousel({
      interval: 1000,
      pause: null
    });
  });