How to decode url-encoded string in javascript

That is not UTF-8, that is percent encoding also known as url encoding.

You can use decodeURIComponent() to convert it back before displaying it

$("#quote1 span").html(decodeURIComponent(text1));

Use either of the following built in JavaScript function to decode any encoded text. No need for jquery or any other library.

const text1 = "Unser platonisches Internetreich droht in die H%E4nde einer bewaffneten Miliz zu fallen."

console.log(decodeURI(text1))

console.log(decodeURIComponent(text1))

update: In case you're wondering how to encode, decoded text, you can use another built in JavaScript function like so

console.log(encodeURI(text1))

console.log(encodeURIComponent(text1))