URL & URLSearchParams

const addr = new URL('https://mysite.com/login?user=someguy&page=news')

// example.com?much=wow
const params = new URLSearchParams(window.location.search)
params.has('much') // true
params.get('much') // 'wow'
params.set('such', 'shiny code')
params.toString() // much=wow&such-shiny+code
for ([key, value] of params) {
  // ...
}
params.delete('much')
params.toString() // such-shiny+code