Detailed explanation of jQuery Ajax uploading files and other data examples using FormData

This article mainly introduces jQuery Ajax's use of FormData to upload files and other data backend web.py acquisition. Friends who need it can refer to it. I hope it can help everyone.

XMLHttpRequest Level 2 adds a new interface - FormData. Compared with ordinary Ajax, the biggest advantage of using FormData is that we can upload binary files asynchronously.

jQuery 2.0+ version supports FormData

Method 1: Use the

form to initialize the FormData object to upload files

•Front end (JQuery):

<form enctype="multipart/form-data">
  <input type="file" name="myfile" onchange="loadFile(this.files[0])">
</form>
<script>
  function loadFile(file){
    var formdata = new FormData($$('form')[0]);
    $.ajax({
      url: 'jobs/add',
      type: 'POST',
      datatype: 'json',
      data: formdata,
      cache:false,
      traditional: true,
      contentType: false,
      processData: false,
      success: function (data) {},
      error: function () {}
    });
  }
</script>

•Backend (web.py):

class Add:
  def POST(self):
    i = web.input(myfile={})
    print(i['myfile'].filename) #文件名
    print(i['myfile'].value) #文件内容
    print(i['myfile'].file.read()) #文件内容

Note:

1. The enctype attribute of needs to be set to "multipart/form-data"

2. The processData, contentType and cache in $.ajax need to be set to false

3. The backend obtains the field name of the file through web.input, which is the same as the name attribute of the input tag specified by the frontend

Method 2√: Instead of , use the FormData object to add fields to upload files

Sometimes, we don’t want to use the

tag, and not only files are passed to the backend through ajax , there may be other key-value pairs, then you can use this method

•Front-end (JQuery):

<input type="file" onchange="loadFile(this.files[0])" />
function loadFile(file){
  container.fd = new FormData();
  container.fd.append('myfile',file);
  container.fd.append('otherkey',othervalue);
  $.ajax({
    url: 'jobs/add',
    type: 'POST',
    datatype: 'json',
    data: fd,
    cache:false,
    traditional: true,
    contentType: false,
    processData: false,
    success: function (data) {},
    error: function () {}
  });
}

•Back-end (web.py):

class Add:
  def POST(self):
    i = web.input(myfile={}, otherkey='')
    print(i['myfile'].filename) #文件名
    print(i['myfile'].value) #文件内容
    print(i['myfile'].file.read()) #文件内容

Note:

1. There is no tag (it’s good to have it)

2. The second parameter of the append() method is the file object. In html, it has been passed through the parameters of the loadFile method

3. The backend obtains the field name of the file through web.input, which is the same as the first parameter of the frontend append() method

4. Because the values ​​obtained through web.input are all strings, if a key-value pair other than a file is passed as null, it will automatically be converted into the string 'null'. You need to pay attention when handling this point

Related recommendations:

Detailed introduction to the FormData object in HTML

How to use FormData to submit forms and upload images

Using FormData in objects in JavaScript

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