たことがある is a set expression in Japanese that is used for saying that ‘there has been a time that I have done (A)’.
The auxiliary verb
た will be added to the verb indicating what you have done, followed by
こと -
が -
ある. Like
の,
こと is regularly used for nominalization (creating a noun-like phrase). However,
の cannot replace
こと in this particular grammar pattern.
-
富士山（ふじさん）へ行（い）ったことがある？
Have you ever been to Mt. Fuji before?
-
私（わたし）はお菓子（かし）を買（か）ったことが無（な）い。
I have never bought snacks.
From these examples, we can see that
ない (the negative equivalent of
ある) may also be used, when you want to express that you have ‘never’ done something.
Just like English, many set phrases cannot be adjusted in Japanese (in the same way that こと cannot be swapped with の in this expression).
In expressions where
こと is followed by a verb phrase,
の may not be used. When used for nominalization,
の is almost always followed by a noun or adjective phrase. Here are some examples.
-
彼（かれ）は踊（おど）ることができる。
He can do things like dance.
-
来週（らいしゅう）は休（やす）みだから旅行（りょこう）へ行（い）くことにする。
Because I have no work next week, I have decided to go traveling.
-
今日（きょう）は帰（かえ）るのが遅（おそ）くなることになる。
Today, I will end up coming home late.