The set() method of the URLSearchParams interface sets the value associated with a given search parameter to the given value. If there were several matching values, this method deletes the others. If the search parameter doesn't exist, this method creates it.


This feature is available in Web Workers.


URLSearchParams.set(name, value)


The name of the parameter to set.
The value of the parameter to set.

Return value



Let's start with a simple example:

let url = new URL('https://example.com?foo=1&bar=2');
let params = new URLSearchParams(url.search);

//Add a third parameter.
params.set('baz', 3);
params.toString(); // "foo=1&bar=2&baz=3"

Below is a real-life example demonstrating how to create a URL and set some search parameters.

You can copy and paste the example in a code environment like Codepen, JSFiddle, or the multi-line JavaScript interpreter in Firefox.

  • line #41: Comment out this line to stop dumping the search parameters to the console (debug()).
  • line #43: Dumps the generated object and its string representation to the console (info()).
  • line #44: Tries to automatically open a new window/tab with the generated URL (when uncommented).
'use strict'

function genURL(rExp, aText, bDebug=false){
	let theURL

	theURL= new URL('https://regexr.com')
	theURL.searchParams.set( 'expression', rExp.toString() )
	theURL.searchParams.set( 'tool', 'replace' )
	theURL.searchParams.set( 'input', '\u2911\u20dc' )// ⤑⃜
	theURL.searchParams.set( 'text', aText.join('\n') )
	if( bDebug ){
		// Display the key/value pairs
		for(var pair of theURL.searchParams.entries()) {
			console.debug(pair[0] + ' = \'' + pair[1] + '\'');
	return theURL
var url = genURL(
	/(^\s*\/\/|\s*[^:]\/\/).*\s*$|\s*\/\*(.|\n)+?\*\/\s*$/gm	// single/multi-line comments
	// /(^\s*\/\/.*|\s*[^:]\/\/.*)/g								// single-line comments
		"These should work:",
		"// eslint-disable-next-line no-unused-vars",
		"lockPref(	'keyword.URL',\t\t'https://duckduckgo.com/html/?q=!+'	)\t//      test",
		"	* bla bla    ",
		"/* bla bla */",
		"// bla bla ",
		"These shouldn\'t work:",
		"var url = \"http://regexr.com/foo.html?q=bar\"",
	, true
console.info( url, url.toString() )
// window.open( url, 'regex_site' )


Specification Status Comment
The definition of 'set()' in that specification.
Living Standard Initial definition.

Browser compatibility

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