HTMLFormElement.enctype
Baseline Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.
HTMLFormElement.enctype 属性常用来指明提交表单的内容类型，可选的值如下：
application/x-www-form-urlencoded: 初始的默认值multipart/form-data: 适用于使用<input>标签上传文件text/plain: HTML5 引入的类型
语法
string = form.enctype form.enctype = string
例子
form.enctype = "application/x-www-form-urlencoded";