1. Expression： Johnny-come-lately
Explanation：A newcomer or late arrival to a group or activity. （新来的人，新手）
Example：The rest of the staff wasn't too fond of Greg, a Johnny-come-lately who received praise from the manager after just one week on the job.
Hurry up, Johnny-come-lately, we've already started today's drills!
This Johnnie-come-lately doesn’t know what it was like in the old days.
Having arrived on the scene relatively recently, Sylva is regarded by many other managers as a Johnny-come-lately.
A: How was today’s work going?
B: Wonderful！I was praised by our manager for more than one time.
A: Good, but remember that as a John-come-lately, you shouold be modest and try to learn from other colleagues.
2. Expression：jump ship
Explanation：By extension, to suddenly abandon any post or task. （突然放弃职位或工作，突然跳槽或更换工作）
Example：I can't believe he resigned and jumped ship before bringing about the big changes he promised.
None of the editors liked the new policies so they all jumped ship as soon as other jobs opened up.
When they realized that the company was in serious financial trouble, quite a few of the staff jumped ship.
We were sure surprised when our vice president jumped ship to work for our biggest competitor. But I can't blame him too much: I hear they're giving him twice the salary he got here.