Block Placement Prevention

Have you ever needed to prevent a specific block from being placed? Sometimes players may aquire dangerous blocks so you can use this script to keep your world or server safe!

Setup ​

Just like other scripts, you need the dependency in your manifest.json. We are using the @minecraft/server module, specifically the latest -beta version.

{
    "format_version": 2,
    "header": {
        "name": "Block Placement Prevention",
        "description": "Prevent Placing of Certain Blocks using Script API",
        "uuid": "6f3a4325-4ce5-42f5-b141-12641c8823c3",
        "min_engine_version": [1, 20, 10],
        "version": "1.0.0"
    },
    "modules": [
        {,
            "type": "data",
            "uuid": "5a080d1d-bef8-47ce-aae1-a2ec3e0010ab",
            "version": "1.0.0"
        },
        {
            "type": "script",
            "language": "javascript",
            "entry": "scripts/main.js",
            "uuid": "53a5804b-fb35-4f7d-a89e-e4a925fadb77",
            "version": [1, 0, 0]
        }
    ],
    "dependencies": [
        {
            // Minecraft native module - needed to use the "@minecraft/server" module
            "module_name": "@minecraft/server",
            "version": "beta"
        }
    ]
}

In our manifest, we have added script module. The entry is where our script file is stored. This is within the scripts folder of the behavior pack. The dependency allows us to use the required script module in our code.

Preventing Placement ​

Even if you are going to use another block, if this is your first time creating this script, follow the tutorial exactly. After you are sure you made the script correctly, you can change the block.

This is because blocks often have an identifier different from what you may think. For example, Glow Item Frames are known internally as minecraft:glow_frame.

We will start by adding the module imports we will be using in the code.

import { world, system } from "@minecraft/server";

After we have added the module, we will add the preventative measure for block placement.

world.beforeEvents.playerPlaceBlock.subscribe((event) => {
    const player = event.source;

    if (event.permutationToPlace.type.id === "minecraft:bedrock") {
        event.cancel = true;
        system.run(() => {
            player.sendMessage("You cannot place Bedrock");
        });
    }
});

This is the main function to execute our code. world.beforeEvents.playerPlaceBlock.subscribe() will run before any block is placed.

• const player = event.source defines the variable player as whatever the source of the event is (the one who is placing the block). const is used over var or let to say that the source cannot be changed, and is constant.
• The if statement requires the criteria to evaluate to true in order for the code within the brackets to run.
  • event.permutationToPlace.type.id === "minecraft:bedrock" verifies that the block being placed is 'minecraft:bedrock'.
• event.cancel = true cancels the placement action that would be performed by this event.
• system.run() is a system call that tells minecraft to push the code being ran to the next tick. This is neccessary as before events cannot modify the state of the world (in our case, sending a message to the player), and using system run makes the code unbound by this limitation. More information on system callbacks & loops can be found here.
• player.sendMessage() sends a message to the player letting them know that they cannot place that block.

Conclusion ​

The message "You cannot place Bedrock" can be modified or replaced with your own logic as needed.

You can also change the identifier of the block being checked in event.permutationToPlace.type.id === "minecraft:bedrock". Put the identifier (with its namespace) in place of minecraft:bedrock.

To learn more about Script API, you can check out the wiki or the Microsoft Docs