What is the use sub_filter directives in Nginx?

The sub_filter directive in Nginx is used to perform substitutions on the response body content. It allows you to search for a specific string or pattern in the response and replace it with another string. This directive is typically used for on-the-fly content modification and rewriting within Nginx.

In short, the main difference between Ajax and a REST API is their purpose and scope:

Ajax (Asynchronous JavaScript and XML): Ajax is a technique used to send and retrieve data from a server asynchronously without requiring a full page reload. It enables dynamic content updates on a web page without disrupting the user experience. Ajax uses JavaScript to make asynchronous HTTP requests to a server and receive responses in various formats, such as JSON or XML.

REST API (Representational State Transfer Application Programming Interface): REST API is an architectural style that defines a set of principles for designing networked applications. It provides a standardized approach for creating, accessing, and manipulating resources over a network. REST APIs are based on HTTP and use the HTTP methods (GET, POST, PUT, DELETE) to perform operations on resources. They typically exchange data in a structured format, such as JSON or XML.