我仍然试图绕过它。
我可以让用户使用文件输入选择文件（甚至多个）：
<form>
<div>
<label>Select file to upload</label>
<input type="file">
</div>
<button type="submit">Convert</button>
</form>
我可以submit使用<fill in your event handler here>. 但是一旦我这样做了，我如何使用 发送文件fetch？
fetch('/files', {
method: 'post',
// what goes here? What is the "body" for this? content-type header?
}).then(/* whatever */);
我是这样做的：
var input = document.querySelector('input[type="file"]')
var data = new FormData()
data.append('file', input.files[0])
data.append('user', 'hubot')
fetch('/avatars', {
method: 'POST',
body: data
})
这是一个带有注释的基本示例。该upload功能是您正在寻找的功能：
// Select your input type file and store it in a variable
const input = document.getElementById('fileinput');
// This will upload the file after having read it
const upload = (file) => {
fetch('http://www.example.net', { // Your POST endpoint
method: 'POST',
headers: {
// Content-Type may need to be completely **omitted**
// or you may need something
"Content-Type": "You will perhaps need to define a content-type here"
},
body: file // This is your file object
}).then(
response => response.json() // if the response is a JSON object
).then(
success => console.log(success) // Handle the success response object
).catch(
error => console.log(error) // Handle the error response object
);
};
// Event handler executed when a file is selected
const onSelectFile = () => upload(input.files[0]);
// Add a listener on your input
// It will be triggered when a file will be selected
input.addEventListener('change', onSelectFile, false);
使用 Fetch API 发送文件的重要说明
需要省略 content-typeFetch 请求的标头。然后浏览器会自动添加Content type包括表单边界的标题，它看起来像
Content-Type: multipart/form-data; boundary=—-WebKitFormBoundaryfgtsKTYLsT7PNUVD
表单边界是表单数据的分隔符
如果你想要多个文件，你可以使用这个
var input = document.querySelector('input[type="file"]')
var data = new FormData()
for (const file of input.files) {
data.append('files',file,file.name)
}
fetch('/avatars', {
method: 'POST',
body: data
})
要提交单个文件，您可以直接使用's数组中的File对象作为初始值设定项中的值：input.filesbody:fetch()
const myInput = document.getElementById('my-input');
// Later, perhaps in a form 'submit' handler or the input's 'change' handler:
fetch('https://example.com/some_endpoint', {
method: 'POST',
body: myInput.files[0],
});