XMLHttpRequestAnsatz

XMLHttpRequest Ansatz is a programming pattern used to perform asynchronous HTTP requests in web applications by using the XMLHttpRequest API. The term is commonly encountered in German-language documentation and discussions of Ajax techniques, where the approach emphasizes explicit creation and management of the XMLHttpRequest instance and its event-driven lifecycle.

Core concepts include creating a new XMLHttpRequest object, calling open(method, url, async), optionally setting request headers with setRequestHeader, and sending data with send. The response is handled via events such as onreadystatechange (traditionally) or onload/onerror (modern usage). The readyState property tracks progress from 0 (uninitialized) to 4 (done), and status reports the HTTP status code. The response data can be read as text via responseText or as XML via responseXML, with JSON typically parsed from responseText.

Advantages of the XMLHttpRequest Ansatz include fine-grained control over request timing, headers, and streaming, as well as wide browser support and compatibility with older libraries. It is a foundational pattern in the Ajax era and remains relevant for low-level tasks, legacy code, or when precise control is required.

Limitations include boilerplate code for common tasks, callback-based asynchronous structure that can complicate logic, and more verbose error handling. It is also more verbose than newer approaches such as the Fetch API and can complicate cross-origin requests without explicit CORS configuration. In modern applications, developers often wrap this pattern in abstractions or migrate to fetch or higher-level libraries. See also Ajax, XMLHttpRequest, Fetch API, CORS, JSON.