I kept reusing the same handful of script conditions across projects, so I figured I'd share them here. These go in Conditional Branch → Script (the last tab), and most work in both MV and MZ unless noted. I'm a RPG Maker MZ dev/user, so I'm more used to it, but a lot of JavaScript stuff is the same on MZ and MV.

All script conditions goes into the command "Conditional Branch...", page 4, script, as the image bellow.

Party & actors

• Check if a specific actor is in the current party:

$gameParty.members().some(a => a.actorId() === 3)

• Check if a specific actor is alive:

$gameActors.actor(3).isAlive()

• Check if the whole party is above half HP (useful before a boss gate):

$gameParty.members().every(a => a.hp >= a.mhp / 2)

• Check the current leader (party member 0):

$gameParty.leader().actorId() === 1

• Check if a specific party member is alive (0 is the leader):

$gameParty.members()[1].isAlive()

Equipment & items

• Check if any party member has a specific weapon equipped:

$gameParty.members().some(a => a.weapons().some(w => w && w.id === 5))

• Check how many of an item the party is carrying:

$gameParty.numItems($dataItems[7]) >= 3

• Check if the party has at least one Key Item (handy for "you're not ready yet" gates):

$gameParty.items().some(item => item.itypeId === 2)

Switches, variables & time

• Check if ALL switches in a range are ON (useful for "collect all X" quests):

[10, 11, 12, 13].every(id => $gameSwitches.value(id))

• Check if ANY switches in a range is ON:

[10, 11, 12, 13].some(id => $gameSwitches.value(id))

• Check if EXACTLY ONE switch in a range is ON:

[10, 11, 12, 13].filter(id => $gameSwitches.value(id)).length === 1

• Check if ALL switches in a range are OFF:

!([10, 11, 12, 13].some(id => $gameSwitches.value(id)))

• Check if a variable is within a range instead of an exact match:

$gameVariables.value(5) >= 10 && $gameVariables.value(5) <= 20

• Check total playtime in seconds (MV/MZ):

$gameSystem.playtime() >= 3600 // 1 hour+

Map & position

• Check if the player is facing a specific direction:

$gamePlayer.direction() === 8 // 2=down, 4=left, 6=right, 8=up

• Check distance between player and an event (in tiles):

$gameMap.distance($gamePlayer.x, $gamePlayer.y, $gameMap.event(5).x, $gameMap.event(5).y) <= 2

• Check if the player is currently on a specific region ID (MZ):

$gamePlayer.regionId() === 4

Misc that saved me a few times

• Check if it's currently night by variable (paired with a day/night plugin):

$gameVariables.value(1) >= 18 || $gameVariables.value(1) < 6 // Var 1 should be the hour, and check if in between 6pm and 6am

• Check gold with a comparison instead of the default Gold condition (lets you use >= inside a bigger expression):

$gameParty.gold() >= 500 && $gameSwitches.value(20)

And...

If you find any // things after two slashes, they are comments and are not considered in JavaScript conditions or anywhere with javascript.

You don't need to be attached to my specific examples. You can mix then, like to know if the player has more gold than the play time (in seconds), you can check:

$gameParty.gold() > $gameSystem.playtime() // or any "useless" check you want

Hope these save someone some time. If you've got your own go-to conditions, drop them below - always happy to steal good ideas.