URLSearchParams

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.

Note: This feature is available in Web Workers.

The URLSearchParams interface defines utility methods to work with the query string of a URL.

URLSearchParams objects are iterable, so they can directly be used in a for...of structure to iterate over key/value pairs in the same order as they appear in the query string, for example the following two lines are equivalent:

for (const [key, value] of mySearchParams) {
}
for (const [key, value] of mySearchParams.entries()) {
}

Although URLSearchParams is functionally similar to a Map, when iterating, it may suffer from some pitfalls that Map doesn't encounter due to how it's implemented.

Constructor

URLSearchParams(): Returns a URLSearchParams object instance.

Instance properties

size Read only: Indicates the total number of search parameter entries.

Instance methods

URLSearchParams[Symbol.iterator](): Returns an iterator allowing iteration through all key/value pairs contained in this object in the same order as they appear in the query string.
URLSearchParams.append(): Appends a specified key/value pair as a new search parameter.
URLSearchParams.delete(): Deletes search parameters that match a name, and optional value, from the list of all search parameters.
URLSearchParams.entries(): Returns an iterator allowing iteration through all key/value pairs contained in this object in the same order as they appear in the query string.
URLSearchParams.forEach(): Allows iteration through all values contained in this object via a callback function.
URLSearchParams.get(): Returns the first value associated with the given search parameter.
URLSearchParams.getAll(): Returns all the values associated with a given search parameter.
URLSearchParams.has(): Returns a boolean value indicating if a given parameter, or parameter and value pair, exists.
URLSearchParams.keys(): Returns an iterator allowing iteration through all keys of the key/value pairs contained in this object.
URLSearchParams.set(): Sets the value associated with a given search parameter to the given value. If there are several values, the others are deleted.
URLSearchParams.sort(): Sorts all key/value pairs, if any, by their keys.
URLSearchParams.toString(): Returns a string containing a query string suitable for use in a URL.
URLSearchParams.values(): Returns an iterator allowing iteration through all values of the key/value pairs contained in this object.

Examples

const paramsString = "q=URLUtils.searchParams&topic=api";
const searchParams = new URLSearchParams(paramsString);

// Iterating the search parameters
for (const p of searchParams) {
  console.log(p);
}

console.log(searchParams.has("topic")); // true
console.log(searchParams.has("topic", "fish")); // false
console.log(searchParams.get("topic") === "api"); // true
console.log(searchParams.getAll("topic")); // ["api"]
console.log(searchParams.get("foo") === null); // true
console.log(searchParams.append("topic", "webdev"));
console.log(searchParams.toString()); // "q=URLUtils.searchParams&topic=api&topic=webdev"
console.log(searchParams.set("topic", "More webdev"));
console.log(searchParams.toString()); // "q=URLUtils.searchParams&topic=More+webdev"
console.log(searchParams.delete("topic"));
console.log(searchParams.toString()); // "q=URLUtils.searchParams"

// Search parameters can also be an object
const paramsObj = { foo: "bar", baz: "bar" };
const searchParams = new URLSearchParams(paramsObj);

console.log(searchParams.toString()); // "foo=bar&baz=bar"
console.log(searchParams.has("foo")); // true
console.log(searchParams.get("foo")); // "bar"

Duplicate search parameters

const paramStr = "foo=bar&foo=baz";
const searchParams = new URLSearchParams(paramStr);

console.log(searchParams.toString()); // "foo=bar&foo=baz"
console.log(searchParams.has("foo")); // true
console.log(searchParams.get("foo")); // bar, only returns the first value
console.log(searchParams.getAll("foo")); // ["bar", "baz"]

No URL parsing

The URLSearchParams constructor does not parse full URLs. However, it will strip an initial leading ? off of a string, if present.

const paramsString1 = "http://example.com/search?query=%40";
const searchParams1 = new URLSearchParams(paramsString1);

console.log(searchParams1.has("query")); // false
console.log(searchParams1.has("http://example.com/search?query")); // true

console.log(searchParams1.get("query")); // null
console.log(searchParams1.get("http://example.com/search?query")); // "@" (equivalent to decodeURIComponent('%40'))

const paramsString2 = "?query=value";
const searchParams2 = new URLSearchParams(paramsString2);
console.log(searchParams2.has("query")); // true

const url = new URL("http://example.com/search?query=%40");
const searchParams3 = new URLSearchParams(url.search);
console.log(searchParams3.has("query")); // true

Preserving plus signs

The URLSearchParams constructor interprets plus signs (+) as spaces, which might cause problems. In the example below, we use hexadecimal escape sequences to mimic a string containing binary data (where every byte carries information) that needs to be stored in the URL search params. Note how the encoded string produced by btoa() contains + and isn't preserved by URLSearchParams.

const rawData = "\x13à\x17@\x1F\x80";
const base64Data = btoa(rawData); // 'E+AXQB+A'

const searchParams = new URLSearchParams(`bin=${base64Data}`); // 'bin=E+AXQB+A'
const binQuery = searchParams.get("bin"); // 'E AXQB A', '+' is replaced by spaces

console.log(atob(binQuery) === rawData); // false

You can avoid this by encoding the data with the encodeURIComponent().

const rawData = "\x13à\x17@\x1F\x80";
const base64Data = btoa(rawData); // 'E+AXQB+A'
const encodedBase64Data = encodeURIComponent(base64Data); // 'E%2BAXQB%2BA'

const searchParams = new URLSearchParams(`bin=${encodedBase64Data}`); // 'bin=E%2BAXQB%2BA'
const binQuery = searchParams.get("bin"); // 'E+AXQB+A'

console.log(atob(binQuery) === rawData); // true

Empty value vs. no value

URLSearchParams doesn't distinguish between a parameter with nothing after the =, and a parameter that doesn't have a = altogether.

const emptyVal = new URLSearchParams("foo=&bar=baz");
console.log(emptyVal.get("foo")); // returns ''
const noEquals = new URLSearchParams("foo&bar=baz");
console.log(noEquals.get("foo")); // also returns ''
console.log(noEquals.toString()); // 'foo=&bar=baz'

Specifications

Specification
URL Standard # urlsearchparams

Browser compatibility

BCD tables only load in the browser