То что прописываю в консоли
let a = "# I open music.yandex.ru\r\n# I click the play button\r\n# I wait until ads pop-up is opened\r\n# I close ads pop-up\r\n# I look at the header\r\n\r\nExpected Result:\r\n{code:java}\r\nТРЕК\r\nYesterday Remastered 2009\r\nИсполнитель: The Beatles{code}"
let b = a.replace(/ (Expected).* */g, "")
console.log(b);


То что выдаёт
# I open music.yandex.ru
# I click the play button
# I wait until ads pop-up is opened
# I close ads pop-up
# I look at the header

Expected Result:
{code:java}
ТРЕК
Yesterday Remastered 2009
Исполнитель: The Beatles{code}