javascript - Jquery FileReader 输入多个图像以缩略图显示

Question

我有图像文件输入，接受多个。另外，我还有 Bootstrap 轮播，用于在上传之前进行一些演示。问题是:我有多个图像，所以我有多个 img src 代码。但是 jquery 只给我提供了 1 个 fileReader 预览。我怎样才能使它成为可能？请帮助我。

jsfiddle https://jsfiddle.net/6gsybxd9/1/

这是我的代码:

<div class="form-group">
    <label>Img (.png/ .gif/ .jpeg):</label>
    <input type="file" multiple="multiple" accept="image/x-png,image/gif,image/jpeg" / id="imgfiles">
</div>


<div class="box thumbnail col-md-2 col-xs-3" style="border-radius:0px">

    <div id="carousel" class="carousel slide" data-ride="carousel">
      <!-- Indicators -->
      <ol class="carousel-indicators"  style="margin-bottom:-15px">
        <li data-target="#carousel" data-slide-to="0" class="active"></li>
        <li data-target="#carousel" data-slide-to="1"></li>
        <li data-target="#carousel" data-slide-to="2"></li>
      </ol>

    <!-- Wrapper for slides -->
    <div class="carousel-inner" role="listbox">
        <div class="item active">
          <img src="http://via.placeholder.com/250x250" id="item_1">
        </div>

        <div class="item">
          <img src="http://via.placeholder.com/250x250" id="item_2">
        </div>

        <div class="item">
          <img src="http://via.placeholder.com/250x250" id="item_3">
        </div>
    </div>

</div> 

和 Jquery 代码:

<script>

function readURL(input) {

  if (input.files && input.files[0]) {
    var reader = new FileReader();

    reader.onload = function(e) {
      $('#item_1').attr('src', e.target.result); //First img
      $('#item_2').attr('src', e.target.result); // Second img
      $('#item_3').attr('src', e.target.result); // Third img
    }

    reader.readAsDataURL(input.files[0]);
  }
}

$("#imgfiles").change(function() {
  readURL(this);
});

</script>

Answer 1

如果用户添加 4、5 或 10 张图像怎么办？
您必须相应地更新您的轮播:

function readURL(input) {

  if (input.files && input.files[0]) {
    var container = $('.carousel-inner').html(''),
      indicators = $('.carousel-indicators').html('');

    for (var f of input.files) {
      var reader = new FileReader();
      reader.onload = function(e) {
        var n = container.children().length;
        container.append(
          `<div class="item ${n ? '' : 'active'}">
            <img src="${e.target.result}">
          </div>`
        );
        indicators.append(
          `<li data-target="#carousel" data-slide-to="${n}" class="${n ? '' : 'active'}"></li>`
        );
      }
      reader.readAsDataURL(f);
    }

  }
}

$("#imgfiles").change(function() {
  readURL(this);
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>
<link href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" rel="stylesheet" />

<div class="form-group">
  <label>Img (.png/ .gif/ .jpeg):</label>
  <input type="file" multiple="multiple" accept="image/*" / id="imgfiles">
</div>

<div class="thumbnail col-md-2 col-xs-3" style="border-radius:0px">

  <div id="carousel" class="carousel slide" data-ride="carousel">
    <!-- Indicators -->
    <ol class="carousel-indicators" style="margin-bottom:-15px">
      <li data-target="#carousel" data-slide-to="0" class="active"></li>
    </ol>

    <!-- Wrapper for slides -->
    <div class="carousel-inner" role="listbox">
      <div class="item active">
        <img src="http://via.placeholder.com/250x250" id="item_1">
      </div>
    </div>

  </div>
</div>