jquery modify upload object

jQuery is a JavaScript library widely used in web development. It provides a rich API and convenient methods to manipulate HTML elements, handle events, create animations, and more. Among them, file upload is a common requirement, and many websites require users to upload pictures, videos and other files. However, due to browser security restrictions, the upload form's style and behavior are default and cannot meet the website's requirements. This article will introduce how to use jQuery to implement the function of modifying uploaded objects to achieve a better user experience.

1. Modify the upload button style

Through the jQuery selector, we can easily get the elements in the upload form and modify their styles. For example, we can hide the default upload button and then add a custom upload button to the page. When the user clicks the custom button, the click event of the default button is actually triggered, thus popping up the file selection box.

HTML code is as follows:

<form action="upload.php" method="post" enctype="multipart/form-data">
  <input type="file" name="fileToUpload" id="fileToUpload">
  <label for="fileToUpload" id="customUpload">选择文件</label>
  <input type="submit" value="上传文件" name="submit">
</form>

CSS code is as follows:

input[type="file"] {
  display: none;
}

#customUpload {
  border: 1px solid #ccc;
  padding: 10px;
  cursor: pointer;
}

In the above code, we set the display attribute of the input[type="file"] element to none , to hide the default upload button. At the same time, we created a label element and set its for attribute to the id of the input[type="file"] element so that the click event of the input element is triggered when the label is clicked. In addition, we also styled the custom upload button to make it look more beautiful and easier to use.

2. Modify the file selection box style

By default, the file selection box is rendered by the browser, and the style and behavior cannot be modified. However, in some modern browsers, we can modify the style of the file selection box through CSS pseudo-class selectors. For example, we can set the pseudo-class selector::-webkit-file-upload-button of the input box (input[type="file"]) to change the text, color, border and other attributes of the file selection box.

CSS code is as follows:

input[type="file"]::-webkit-file-upload-button {
  background-color: #42a5f5;
  color: #fff;
  padding: 10px;
  border: none;
  border-radius: 5px;
  cursor: pointer;
}

In the above code, we set the pseudo-class selector::-webkit-file-upload-button for the input[type="file"] element Background color, text color, border style and other attributes to make it look more beautiful.

3. Modify the progress bar and prompt information when uploading files

When uploading files, we also need to display the upload progress bar and prompt information to the user to let the user know the upload status and progress. In jQuery, we can use AJAX and XMLHttpRequest objects to upload files, and obtain upload progress and results through callback functions. The specific steps are as follows:

(1) Create a FormData object and add files and other form data to it.

(2) Use the $.ajax() function to send an AJAX request, set type to POST, url to the upload address, data to the FormData object, and processData and contentType to false to process binary data.

(3) Set the xhr.upload.onprogress callback function, monitor the upload progress, and update the width of the progress bar in the callback function.

(4) Set the xhr.onreadystatechange callback function, monitor the upload status and results, and update the prompt information and processing results in the callback function.

The JavaScript code is as follows:

$(document).on('change', '#fileToUpload', function() {
  var file = $(this)[0].files[0];
  var formData = new FormData();
  formData.append('file', file);
  $.ajax({
    type: 'POST',
    url: 'upload.php',
    data: formData,
    processData: false,
    contentType: false,
    xhr: function() {
      var xhr = new XMLHttpRequest();
      xhr.upload.onprogress = function(e) {
        if (e.lengthComputable) {
          var percent = Math.round((e.loaded / e.total) * 100);
          $('#progress').css('width', percent + '%');
          $('#percent').text(percent + '%');
        }
      };
      return xhr;
    },
    success: function(data) {
      $('#result').text('上传成功');
      // 处理上传结果
    },
    error: function(XMLHttpRequest, textStatus, errorThrown) {
      $('#result').text('上传失败');
      // 处理上传错误
    }
  })
});

In the above code, we listen to the change event of the input[type="file"] element in order to obtain the uploaded file object and add it to the FormData object middle. We then use the $.ajax() function to send the AJAX request and set the upload progress and status callback functions for the xhr object. In the upload progress callback function, we calculate and update the width and prompt information of the progress bar. In the success or failure callback function, we update the upload results and process the upload results.

Summary

By using jQuery, we can easily implement the function of modifying the uploaded object, improving user experience and website interactivity. Among them, it should be noted that although the style and behavior of the upload form can be modified, ensuring the security and stability of the upload is the most important consideration. Therefore, in the process of modifying the upload object, we should follow relevant specifications and best practices to ensure the correctness and stability of the upload function.

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