JavaScript multiplayer functions

Use these helpers when a game rule must address more than the current visitor. Build and test the single-player version first, then decide exactly what should be shared.

Know your data types

Data type	Use it for	Example
Per-player parameter	A separate role, team, or slot for every player	Role = Explorer
Multiplayer numeric variable	One shared counter or score	TeamScore = 14
Multiplayer task	One shared stage of a round	RoundStarted = Active

Do not use the same name for different scopes.

Get the current player list

{{Players}} resolves to the players currently in the room. Pass it to the player-list helpers:

const players = {{Players}};
SetPlayersParameters(players, 'Role', 'Explorer');

Supported player-list helpers

Function	Purpose
AssignNumbersInOrder(players, name)	Give players sequential numbers beginning at 1.
SelectRandomPlayers(players, count)	Choose a subset of a player list.
SelectPlayers(players, name, value)	Filter a list by a per-player parameter.
SelectPlayersParameters(players, name)	Return parameter values from a player list.
SetPlayersParameters(players, name, value)	Set a parameter on every player in a list.
SetPlayerParameter(name, value)	Set a parameter on the current player.
SelectPlayerParameter(name)	Read a parameter on the current player.
CountArray(list)	Count entries in a player list.
PrintString(list)	Turn a list into comma-separated text.

Assign player slots

AssignNumbersInOrder({{Players}}, 'Slot');

Run this from one deliberate round-start path. Do not put it in a script that re-runs for every state change unless reassigning slots is intended.

Pick a role

const seeker = SelectRandomPlayers({{Players}}, 1);
SetPlayersParameters(seeker, 'Role', 'Seeker');

Test this with the smallest and largest room sizes your game supports. Selecting a role each time a player joins will produce unstable results unless that is your game design.

Filter and count

const blueTeam = SelectPlayers({{Players}}, 'Team', 'Blue');
const readyBluePlayers = SelectPlayers(blueTeam, 'Ready', true);

if (CountArray(readyBluePlayers) >= 2) {
  SetTask('BlueTeamReady', 'Active', 0);
}

Make sure the value you filter on matches the value you set. For example, true is different from the text 'true'.

Turn player values into readable text

SelectPlayersParameters() returns a list. Use PrintString() when you need a single text value from that list:

const blueTeam = SelectPlayers({{Players}}, 'Team', 'Blue');
const teamLabels = SelectPlayersParameters(blueTeam, 'Team');
SetVariable('BlueTeamLabels', PrintString(teamLabels), 0);

PrintString() returns comma-separated text. It expects a list; do not use it as a developer log or pass it one plain text value. Every player in that list must have the requested parameter, so filter the list by that same configured parameter first.

Shared score recipe

Create TeamScore as a multiplayer numeric variable, then use the server-backed update helper:

UpdateMultiplayerNumericVariable('TeamScore', 1, 1, 0);

The operation values are:

Operation	Meaning
0	Set
1	Add
2	Subtract
3	Multiply
4	Divide

Use Add for each scored event. This avoids a local read-modify-write race when two players score at nearly the same time.

Shared score and timer leaderboard recipe

Start the named timer through the no-code Start Timer effect when the round begins.
Increment the multiplayer TeamScore using the Add operation.
Stop the timer and post or display the result with the dedicated no-code leaderboard effects.
Test two players scoring at the same time, a late join, and a round ending during an update.

Keep the timer and leaderboard setup in no-code effects. JavaScript Function should contain only the small rule that changes shared state.

Safe defaults

Run player assignment from one explicit task rather than a repeating state-change script.
Use stable names for parameters, tasks, and shared variables.
Test with multiple real players before publishing.
Keep player IDs inside the helpers; do not guess or hard-code another player’s ID.

Code & Custom UI