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Submit a form with Ajax

Written byPhuoc Nguyen
17 Mar, 2020
Level 1 — Basic
The following function submits the data of `formEle` to the back-end using an Ajax request:
const submit = function (formEle) {
return new Promise(function (resolve, reject) {
// Serialize form data
// See https://phuoc.ng/html-dom/serialize-form-data-into-a-query-string
const params = serialize(formEle);

// Create new Ajax request
const req = new XMLHttpRequest();
req.open('POST', formEle.action, true);
req.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded; charset=UTF-8');

// Handle the events
req.onload = function () {
if (req.status >= 200 && req.status < 400) {
req.onerror = function () {

// Send it
Where the `serialize` function serializes all the form data into a query string. You can see how it's implemented in this post.


const formEle = document.getElementById(...);

submit(formEle).then(function(response) {
// `response` is what we got from the back-end
// We can parse it if the server returns a JSON
const data = JSON.parse(response);

See also

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