The onreadystatechange event is an event that is raised when a web page's state changes, such as when a form is submitted or when an AJAX request is completed. It is called in JavaScript, which is the programming language that is used to create and manipulate web pages. The onreadystatechange event is triggered whenever the state of the page changes, and it has a single property called readyState. This property is an integer that indicates the current state of the event. For example, if the page has been loaded and the readyState property is equal to 4, then the page has completed its loading process and is ready to be displayed. The onreadystatechange event is called in JavaScript using the addEventListener method, which is provided by the browser. The addEventListener method takes a function as an argument, which is called whenever the readyState property changes. This function is responsible for updating the content of the page or performing other actions based on the new state of the page. The onreadystatechange event follows the camelCase convention because it is named after the property that is being changed. The convention is to capitalize the first letter of each word in a property name, except for the first letter of the word that is being added to the property name. For example, the onreadystatechange event would be named onreadystatechangeProperty. In summary, the onreadystatechange event follows the camelCase convention because it is named after the property that is being changed. This convention is used in JavaScript to ensure that event handlers are properly named and organized, making it easier to understand and maintain the code.