Add .pick() and .exclude()

index.d.ts

@@ -404,3 +404,40 @@ export function stringifyUrl(
 	object: UrlObject,
 	options?: StringifyOptions
 ): string;
+
+/**
+Filter query parameters from a url.
+
+@param url The url containing the query parameters to filter.
+@param includeParams The names of the query parameters to retain. All other query parameters will be removed from the url.
+@param filter A filter predicate that will be provided the name of each query parameter and its value.
+
+@example
+```
+queryString.filterElements('https://foo.bar?foo=1&bar=2#hello', ['foo']);
+//=> 'https://foo.bar?foo=1#hello'
+
+queryString.filterElements('https://foo.bar?foo=1&bar=2#hello', (name, value) => value === 2, {parseNumbers: true});
+//=> 'https://foo.bar?bar=2#hello'
+```
+*/
+export function filterElements(
+	url: string,
+	includeParams: ReadonlyArray<string>,
+	options?: ParseOptions & StringifyOptions
+): string
+export function filterElements(
+	url: string,
+	filter: (name: string, value: string | boolean | number) => boolean,
+	options?: {parseBooleans: true, parseNumbers: true} & ParseOptions & StringifyOptions
+): string
+export function filterElements(
+	url: string,
+	filter: (name: string, value: string | boolean) => boolean,
+	options?: {parseBooleans: true} & ParseOptions & StringifyOptions
+): string
+export function filterElements(
+	url: string,
+	filter: (name: string, value: string | number) => boolean,
+	options?: {parseNumbers: true} & ParseOptions & StringifyOptions
+): string

index.js

@@ -2,6 +2,7 @@
 const strictUriEncode = require('strict-uri-encode');
 const decodeComponent = require('decode-uri-component');
 const splitOnFirst = require('split-on-first');
+const filterObject = require('filter-obj');
 
 const isNullOrUndefined = value => value === null || value === undefined;
 
@@ -376,3 +377,16 @@ exports.stringifyUrl = (input, options) => {
 
 	return `${url}${queryString}${hash}`;
 };
+
+exports.filterElements = (input, filter, options) => {
+	options = Object.assign({
+		parseFragmentIdentifier: true
+	}, options);
+
+	const {url, query, fragmentIdentifier} = exports.parseUrl(input, options);
+	return exports.stringifyUrl({
+		url,
+		query: filterObject(query, filter),
+		fragmentIdentifier
+	}, options);
+};

package.json

@@ -34,10 +34,12 @@
 		"stringify",
 		"encode",
 		"decode",
-		"searchparams"
+		"searchparams",
+		"filter"
 	],
 	"dependencies": {
 		"decode-uri-component": "^0.2.0",
+		"filter-obj": "^1.1.0",
 		"split-on-first": "^1.0.0",
 		"strict-uri-encode": "^2.0.0"
 	},

readme.md

@@ -415,6 +415,43 @@ Type: `object`
 
 Query items to add to the URL.
 
+### .filterElements(url, includeParams, options?)
+### .filterElements(url, filter, options?)
+
+Filter query parameters from a url.
+
+```js
+queryString.filterElements('https://foo.bar?foo=1&bar=2#hello', ['foo']);
+//=> 'https://foo.bar?foo=1#hello'
+
+queryString.filterElements('https://foo.bar?foo=1&bar=2#hello', (name, value) => value === 2, {parseNumbers: true});
+//=> 'https://foo.bar?bar=2#hello'
+```
+
+#### url
+
+Type: `string`
+
+The url containing the query parameters to filter.
+
+#### includeParams
+
+Type: `string[]`
+
+The names of the query parameters to retain. All other query parameters will be removed from the url.
+
+#### filter
+
+Type: `(name, value) => boolean`
+
+A filter predicate that will be provided the name of each query parameter and its value. The predicate will be provided with the `name` of the query parameter and its `value`. The `parseNumbers` and `parseBooleans` options affect `value`.
+
+#### options
+
+Type: `object`
+
+[Parse options](#options) and [stringify options](#options-1).
+
 ## Nesting
 
 This module intentionally doesn't support nesting as it's not spec'd and varies between implementations, which causes a lot of [edge cases](https://github.com/visionmedia/node-querystring/issues).

test/filter-elements.js

@@ -0,0 +1,17 @@
+import test from 'ava';
+import queryString from '..';
+
+test('filters elements in a url with a filter array', t => {
+	t.is(queryString.filterElements('http://example.com/?a=1&b=2&c=3#a', ['a', 'b']), 'http://example.com/?a=1&b=2#a');
+});
+
+test('filters elements in a url with a filter predicate', t => {
+	t.is(queryString.filterElements('http://example.com/?a=1&b=2&c=3#a', (name, value) => {
+		t.is(typeof name, 'string');
+		t.is(typeof value, 'number');
+
+		return name === 'a';
+	}, {
+		parseNumbers: true
+	}), 'http://example.com/?a=1#a');
+});