How to extract some properties from an array of object?

[pagaille]

True. However, my brain feels more adapted to the JSONata way of doing this, probably because it's more visual (and that's also why I love coding in NodeRed). @ghayne 's solution works brilliantly by the way :

$map(
   payload,
   function($v,$i) {
       [{
           "time":$toMillis($v.TimeStamp),
           "Power":$v.Power
       }] 
   }
)

Since I asked preferably the JSONata code, I think he deserves the "solution" tag, but thank you both of you really for your support.

Matthieu