Array : merge 2 array and add a new item if key exists

Array : merge 2 array and add a new item if key exists
To Access My Live Chat Page,
On Google, Search for "hows tech developer connect"

As promised, I'm going to share a hidden feature with you.
This is a YouTube's feature which works on Desktop.
First, Make sure this video is playing.
After that, type the word 'awesome' on your keyboard.
It will change your youtube progress bar into a flashing rainbow.

A short overview of who I am,
Hey, I am Delphi.
Let me help you with your questions.
Array : merge 2 array and add a new item if key exists
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merge array item Array exists : new add and if 2 a key