URLSearchParams

URLSearchParams is a Web API interface that provides convenient access to the query component of a URL. It represents the query string as an ordered list of key-value pairs and supports reading, adding, removing, and updating parameters without manual string manipulation. It is part of the WHATWG URL API and is implemented in all major browsers and in Node.js.

Construction and mutability: URLSearchParams can be created from a query string, from an existing URLSearchParams, or from an iterable of [name, value] pairs. If the input begins with a question mark, the mark is ignored. The instance is mutable, so changes affect the serialized form returned by toString() and can be reflected in the URL.

Core methods and properties: The interface includes append(name, value) to add a parameter, delete(name) to remove all values for a name, get(name) to retrieve the first value, getAll(name) to retrieve all values, has(name) to check for presence, set(name, value) to replace values, and sort() to order parameters by name. It also exposes length and provides iterators keys(), values(), and entries(); the object is iterable via for...of.

Iteration and serialization: toString() returns a percent-encoded query string representing the current parameters, using UTF-8 encoding (spaces become %20). The object can be used to build URLs or fetch requests by appending the serialized string to a base URL or by syncing with url.searchParams.

Compatibility and usage: URLSearchParams is widely supported in modern browsers and available in Node.js. It is commonly used to read location.search, modify query parameters, and construct new request URLs in web applications.