Question

请参见以下代码

https://codepen.io/manuchadha/pen/PBKYBJ

我创建了一个表格。我希望能够使用文件上传输入来上传图像。选择图像后，我想在文件选择器框的正下方显示图像的缩略图，并在图像的右上角显示一个关闭（x）标记，该标记可用于删除图像。但是我无法创建它。我在做什么错了？

HTML

<!DOCTYPE html>
<html lang="en">
<head>
  <base href=""> 
  <title>Example</title>
  <!--meta http-equiv="Content-Security-Policy" content="default-src *; style-src 'self' 'unsafe-inline'; script-src 'self' 'unsafe-inline' 'unsafe-eval'"-->
  <link rel="stylesheet" media="screen" href="fiddle.css">

<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.1.1/css/bootstrap.min.css">
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/bootstrap-select/1.13.1/css/bootstrap-select.css" />
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="fiddle.js"></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.1.1/js/bootstrap.bundle.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/bootstrap-select/1.13.1/js/bootstrap-select.min.js"></script>


</head>
<body>

  <div id="form-div" class="body__div--background"> <!-- takes the complete width/height of content section -->
    <!-- The novalidate attribute in the <form> element prevents the browser from attempting native HTML validations.
    validation will be done using Angular's Validators which come with FormGroups and FormControls-->
    <form id="new-question-form" class="practice-question-form" [formGroup]="practiceQuestionForm" (ngSubmit)="addPracticeQuestion()" novalidate>
      <!-- label and small in same line. select in a new line, thus enclosed select in a div-->
      <div class="form-group">

      <div class="form-group">
        <label for="file-upload" class="control-label required">Upload files</label>

        <div class="custom-file" id="file-upload" lang="es">
          <input type="file" class="custom-file-input" id="question-file-upload" onchange="handleFileSelect()">
          <label class="custom-file-label" for="question-file-upload">
            Select file...
          </label>        
        </div>
      </div>

  <button type="submit"  id="submit-practice-question-button" class="content-div__button--blue"> Submit! </button>
    </form>
    <div id="imageContainer">
      </div>
      </div>
</div> 
</body>

CSS

body{
  margin:0px;
}

.body__div--background {
  background: linear-gradient(45deg,#33b1f8 37%,#6e90f6 100%); /*syntax linear-gradient(direction, color1 limit, color2 limit)*/
  color:#555555;
  font-family: Helvetica;
  line-height:1.5;
  font-size: 11px;
  letter-spacing: 0.25px;
}




#submit-practice-question-button{
  display:block;
}

#imageContainer{
  display:inline-block;
  border: 1px solid black;
}

.close {
  top:0;
  right:80; /*match the width of the image*/
  position: relative;
  opacity: 0.3;
}
.close:hover {
  opacity: 1;
}
.close:before, .close:after {
  position: relative;

  left: 15px;
  content: ' ';
  height: 33px;
  width: 2px;
  background-color: #333;
}
.close:before {
  transform: rotate(45deg);
}
.close:after {
  transform: rotate(-45deg);
}

JS

 /*handler for file upload*/
  function handleFileSelect(){
    console.log("got file upload event:");
    /*
     FileList object is the object returned as a result of a user selecting files using the <input> element,
     from a drag and drop operation's DataTransfer object, or from the mozGetAsFile() API on an HTMLCanvasElement.
     */
    var files = document.getElementById('question-file-upload').files;//event.target.files;
    console.log("files selected:"+files+", total selected: "+files.length);
    for(var i=0;i<files.length;i++)
    {
      console.log("files name:"+files[i].name)
      console.log("files object:"+files[i])
    }

    //working with only 1 file at the moment
    var file = files[0];

    if (files && file) {
      /*
      The FileReader object lets web applications asynchronously read the contents of files (or raw data buffers) stored on the user's computer,
      using File or Blob objects to specify the file or data to read.
       */
      var reader = new FileReader();

      /*bind onload event of FileReader to _handleReaderLoaded
      onload is a handler for the load event. This event is triggered by FileReader each time the reading operation is successfully completed.
       */
      reader.onload =this._handleReaderLoaded.bind(this);

      reader.readAsBinaryString(file);
    }
  }

  function _handleReaderLoaded(readerEvt) {
    var binaryString = readerEvt.target.result;
    var base64textString= btoa(binaryString);
    console.log(btoa(binaryString));
    var src = "data:image/png;base64,";
    src += base64textString;

    var newImage = document.createElement('img');
    newImage.src = src;
    newImage.width = newImage.height = "80";
    var closeButtonLink = document.createElement('a');
   closeButtonLink.setAttribute('href',"#"); 
 closeButtonLink.classList.add("close");   
document.querySelector('#imageContainer').appendChild = newImage;
    document.querySelector('#imageContainer').appendChild = closeButtonLink;


  }

Answer 1

appendChild是一种方法，而不是属性。

例如，应该使用node.appendChild = newImage;代替node.appendChild(newImage);

您还需要在锚标记中添加“ X”。我将其包含在下面的示例中。

另一件事，我也做了一个小的性能提升，您将对查询的引用保存在变量中，因此您无需两次查询DOM。

var closeButtonLink = document.createElement('a');
closeButtonLink.textContent = "X";
closeButtonLink.setAttribute('href', "#");
closeButtonLink.classList.add("close");

// use a var here to only query once for imageContainer
var imgc = document.querySelector('#imageContainer');
imgc.appendChild(newImage);
imgc.appendChild(closeButtonLink);

无法使用关闭按钮从图像创建缩略图

1 个答案: