The XMLHttpRequest.withCredentials property is a Boolean that indicates whether or not cross-site Access-Control requests should be made using credentials such as cookies, authorization headers or TLS client certificates. Setting withCredentials has no effect on same-site requests.
The append() method of the FormData interface appends a new value onto an existing key inside a FormData object, or adds the key if it does not already exist.
The FormData.entries() method returns an iterator allowing to go through all key/value pairs contained in this object. The key of each pair is a USVString object; the value either a USVString, or a Blob.
The get() method of the FormData interface returns the first value associated with a given key from within a FormData object. If you expect multiple values and want all of them, use the getAll() method instead.
The set() method of the FormData interface sets a new value for an existing key inside a FormData object, or adds the key/value if it does not already exist.
The FormData object lets you compile a set of key/value pairs to send using XMLHttpRequest. It is primarily intended for use in sending form data, but can be used independently from forms in order to transmit keyed data. The transmitted data is in the same format that the form's submit() method would use to send the data if the form's encoding type were set to multipart/form-data.
An EventHandler that is called whenever the readyState attribute changes. The callback is called from the user interface thread. The XMLHttpRequest.onreadystatechange property contains the event handler to be called when the readystatechange event is fired, that is every time the readyState property of the XMLHttpRequest changes. The callback is called from the user interface thread.
The XMLHttpRequest.send() method sends the request. If the request is asynchronous (which is the default), this method returns as soon as the request is sent. If the request is synchronous, this method doesn't return until the response has arrived. send() accepts an optional argument for the request body. If the request method is GET or HEAD, the argument is ignored and request body is set to null.
The XMLHttpRequest.upload property returns an XMLHttpRequestUpload object, representing the upload process. It is an opaque object, but being an XMLHttpRequestEventTarget, event listeners can be set on it to track its process.
XMLHttpRequestEventTarget is the interface that describes the event handlers you can implement in an object that will handle events for an XMLHttpRequest.
The XMLHttpRequest.abort() method aborts the request if it has already been sent. When a request is aborted, its readyState is set to 0 (UNSENT), but the readystatechange event is not fired.