Let\'s say I have this element on the page:
This will create a button that allows the users
You can use fetch optionally with await-try-catch
let photo = document.getElementById("image-file").files[0];
let formData = new FormData();
formData.append("photo", photo);
fetch('/upload/image', {method: "POST", body: formData});
async function SavePhoto(inp)
{
let user = { name:'john', age:34 };
let formData = new FormData();
let photo = inp.files[0];
formData.append("photo", photo);
formData.append("user", JSON.stringify(user));
try {
let r = await fetch('/upload/image', {method: "POST", body: formData});
console.log('HTTP response code:',r.status);
} catch(e) {
console.log('Huston we have problem...:', e);
}
}
<input id="image-file" type="file" onchange="SavePhoto(this)" >
<br><br>
Before selecting the file open chrome console > network tab to see the request details.
<br><br>
<small>Because in this example we send request to https://stacksnippets.net/upload/image the response code will be 404 ofcourse...</small>
<br><br>
(in stack overflow snippets there is problem with error handling, however in <a href="https://jsfiddle.net/Lamik/b8ed5x3y/5/">jsfiddle version</a> for 404 errors 4xx/5xx are <a href="https://stackoverflow.com/a/33355142/860099">not throwing</a> at all but we can read response status which contains code)
Old school approach - xhr
let photo = document.getElementById("image-file").files[0]; // file from input
let req = new XMLHttpRequest();
let formData = new FormData();
formData.append("photo", photo);
req.open("POST", '/upload/image');
req.send(formData);
function SavePhoto(e)
{
let user = { name:'john', age:34 };
let xhr = new XMLHttpRequest();
let formData = new FormData();
let photo = e.files[0];
formData.append("user", JSON.stringify(user));
formData.append("photo", photo);
xhr.onreadystatechange = state => { console.log(xhr.status); } // err handling
xhr.open("POST", '/upload/image');
xhr.send(formData);
}
<input id="image-file" type="file" onchange="SavePhoto(this)" >
<br><br>
Choose file and open chrome console > network tab to see the request details.
<br><br>
<small>Because in this example we send request to https://stacksnippets.net/upload/image the response code will be 404 ofcourse...</small>
<br><br>
(the stack overflow snippets, has some problem with error handling - the xhr.status is zero (instead of 404) which is similar to situation when we run script from file on <a href="https://stackoverflow.com/a/10173639/860099">local disc</a> - so I provide also js fiddle version which shows proper http error code <a href="https://jsfiddle.net/Lamik/k6jtq3uh/2/">here</a>)
SUMMARY
filename
formData parameter. Content-Type
to multipart/form-data
- this will be set automatically by browser. /upload/image
you can use full address like http://.../upload/image
. multiple
attribute: <input multiple type=... />
, and attach all chosen files to formData in similar way (e.g. photo2=...files[2];
... formData.append("photo2", photo2);
)let user = {name:'john', age:34}
in this way: formData.append("user", JSON.stringify(user));
Unless you're trying to upload the file using ajax, just submit the form to /upload/image
.
<form enctype="multipart/form-data" action="/upload/image" method="post">
<input id="image-file" type="file" />
</form>
If you do want to upload the image in the background (e.g. without submitting the whole form), you can use ajax: