How does Ajax achieve interaction between the front and backend?

Ajax is a technology used in web development that allows for data interaction with a server without the need to refresh the entire page. The following are the basic steps for implementing front-end and back-end interaction with Ajax:

1. To create an XMLHttpRequest object: In JavaScript, the XMLHttpRequest object is used to send HTTP requests and receive responses from the server. You can create an XMLHttpRequest object using the following code:

var xmlhttp = new XMLHttpRequest();

1. Establishing a connection to the server: Use the open() method to specify the type (GET or POST) and URL of the HTTP request. For example, sending a GET request:

xmlhttp.open("GET", "example.php", true);

1. Send request: Use the send() method to send the request to the server. For example, send a GET request.

xmlhttp.send();

1. Handling server response: Use the onreadystatechange event to listen for the server’s response, and use the responseText or responseXML properties to retrieve the response content. For example, handling a response to a GET request:

xmlhttp.onreadystatechange = function() {
  if (xmlhttp.readyState === 4 && xmlhttp.status === 200) {
    var response = xmlhttp.responseText;
    // 处理响应数据
  }
};

1. Handle response data: Perform corresponding operations based on the response data from the server, such as displaying the data on the page.

document.getElementById("result").innerHTML = response;

The above are the basic steps for implementing front-end and back-end interaction with Ajax, which can be adjusted and expanded according to actual requirements.