URLSearchParams

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

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

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

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

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

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

// Having duplicate parameters only returns the first value
let paramStr = 'foo=bar&foo=baz';
let searchParams = new URLSearchParams(paramStr);

searchParams.toString();                 // "foo=bar&foo=baz"
searchParams.has('foo');                 // true

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

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

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

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

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

const base64 = btoa(String.fromCharCode(19, 224, 23, 64, 31, 128)); // base64 is "E+AXQB+A"
const searchParams = new URLSearchParams('q=foo&bin=' + base64); // q=foo&bin=E+AXQB+A
const getBin = searchParams.get('bin'); // "E AXQB A" + char is replaced by spaces
btoa(atob(getBin)); // "EAXQBA==" no error thrown
btoa(String.fromCharCode(16,5,208,4)) // "EAXQBA==" decodes to wrong binary value
getBin.replace(//g, '+'); // "E+AXQB+A" is one solution

// or use set to add the parameter, but this increases the query string length
searchParams.set('bin2', base64) // "q=foo&bin=E+AXQB+A&bin2=E%2BAXQB%2BA" encodes + as %2B
searchParams.get('bin2'); // "E+AXQB+A"

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