What is the difference between Onreadystatechange and onload?

A readystatechange occurs several times in the life of a request as it progresses to different phases, but a load event only occurs when the request has successfully completed. If you’re not interested in detecting intermediate states or errors, then onload might be a good choice.

What does Onreadystatechange mean?

The onreadystatechange property defines a function to be executed when the readyState changes. The status property and the statusText property holds the status of the XMLHttpRequest object.

What is this readyState == 4 && this status == 200?

readyState: 4: request finished and response is ready status: 200: “OK” When readyState is 4 and status is 200, the response is ready: since when xmlhttp.

What is XHR readyState?

The XMLHttpRequest.readyState property returns the state an XMLHttpRequest client is in. An XHR client exists in one of the following states: Value. State. Description.

What are different readyState in AJAX?

readyState = 0 After you have created the XMLHttpRequest object, but before you have called the open() method….readyState.

State Description
0 The request is not initialized.
1 The request has been set up.
2 The request has been sent.
3 The request is in process.

How many readyState statuses are present in AJAX?

readyState = 2 After you have called send(). readyState = 3 After the browser has established a communication with the server, but before the server has completed the response….readyState.

State Description
2 The request has been sent.
3 The request is in process.
4 The request is completed.


XHR is the XMLHttpRequest Object which interacts with the server. Ajax technique in the nutshell leverages the XHR request to send and receive data from the webserver. This object is provided by the browser’s javascript environment. It transfers the data between the web browser and server.

Why is readyState 4?

State 4 means that the request had been sent, the server had finished returning the response and the browser had finished downloading the response content. So, it is right to say that the AJAX call has completed.

What is the difference between XHR and AJAX?

Ajax allows us to send and receive data from the webserver asynchronously without interfering with the current state or behavior of the web page or application. XHR is the XMLHttpRequest Object which interacts with the server.

What is the disadvantages of AJAX?

The disadvantages of AJAX are: – Search engines would not be able to index an AJAX application. – The server information can not be accessed within AJAX. – AJAX is not well integrated with any browser.

What is postback in AJAX?

Using ajax we can send and receive data from server with our reloading the page(postback). So the page will nor refresh if a server call encounters.

How do I know if WebSocket is working?

Checking websocket for successful connection in JavaScript You can check if a WebSocket is connected by doing either of the following: Specifying a function to the WebSocket. onopen event handler property, or; Using addEventListener to listen to the open event.

What is responseText in AJAX?

The responseText method is used for all formats that are not based on XML. It returns an exact representation of the response as a string. Plain text, (X)HTML, and JSON are all formats that use responseText.

What is ready state 4 AJAX?

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