POST request from a Splunk app using the @splunk/splunk-utils package

splunkapp-post.js

import * as config from '@splunk/splunk-utils/config';
import { createRESTURL } from '@splunk/splunk-utils/url';
import { handleError, handleResponse } from '@splunk/splunk-utils/fetch';

...

const url = createRESTURL(
    'storage/collections/data/mycollection/key',
    { app: config.app, sharing: 'app' }
);
fetch(url, {
    method: 'POST',
    credentials: 'include',
    headers: {
        'X-Splunk-Form-Key': config.CSRFToken,
        'X-Requested-With': 'XMLHttpRequest',
        'Content-Type': 'application/json',
    },
    body: JSON.stringify(data),
}).then(handleResponse(200))
.then((json) => {
    // success case - do something 
}, handleError('Error updating. Please try again.'))
.catch((errMsg) => {
    // error case - print `errMsg` to the user
});