Block Placement Prevention

Ever need to prevent a specific block from being placed? In 1.20.10, some dangerous unobtainable blocks can be acquired, 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 version 1.4.0-beta.

{
	"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": [
		{
			"description": "Behavior Pack Module",
			"type": "data",
			"uuid": "5a080d1d-bef8-47ce-aae1-a2ec3e0010ab",
			"version": [1, 0, 0]
		},
		{
			"description": "Gametest Module",
			"type": "script",
			"language": "javascript",
			"entry": "scripts/index.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": "1.4.0-beta"
		}
  ]
}

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

First Preventative Measure #

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.

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

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

world.beforeEvents.itemUseOn.subscribe(event => {
    if (event.itemStack.typeId === "minecraft:bedrock" && event.block.typeId != "minecraft:frame" && event.block.typeId != "minecraft:glow_frame") {
        event.cancel = true;
        system.run(() => {
            const player = event.source
            player.sendMessage(`You cannot place Bedrock`)
        });
    }
});

This is the main function to execute our commands. world.beforeEvents.itemUseOn.subscribe() will run before any item is used

• The if() statement required criteria to be met in order for the next section of the script to run
  • event.itemStack.typeId === "minecraft:bedrock" verifies that the item being used is minecraft:bedrock
  • event.block.typeId != "minecraft:frame" && event.block.typeId != "minecraft:glow_frame" checks that the block being targeted is not an item frame, so that the block whose placement is being canceled can still be placed in item frames.
    • If you know what you are doing, you can skip this statement so that it can't be placed in item frames. That would also negate the need for the next preventative measure.
• event.cancel = true cancels the action that would be done with the item, whether placing the block, editing a sign, or opening a chest. It would be possible to allow interactions with all blocks in a similar way to item frames, but I skipped it for the sake of brevity.
• const player = event.source sets up the constant that player is whatever the source of the event is. Constants cannot be changed, unlike variables.
• player.sendMessage() sends a message to the player letting them know that they cannot place that block. The message You cannot place Bedrock can be modified as necessary.

Second Preventative Measure #

This script will work fine in most cases, but it does have a flaw. Since it does not cancel that item use if the targeted block is an item frame, simply sneaking will allow the block to be placed on top or to the side of the frame. We need to prevent this.

We will use a very similar script.

world.beforeEvents.itemUseOn.subscribe(event => {
    if (event.itemStack.typeId === "minecraft:bedrock" && event.source.isSneaking === true) {
        event.cancel = true;
        system.run(() => {
            const player = event.source
            player.sendMessage(`You cannot place Bedrock`)
        });
    }
});

There is only one change to the script. Instead of detecting if you are not targeting an item frame, this if() statement checks if the source is sneaking. This is prevents the specific block from being used while a player is sneaking, thus keeping them from placing it on item frames.

Conclusion #

This should be your entire script:

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

world.beforeEvents.itemUseOn.subscribe(event => {
    if (event.itemStack.typeId === "minecraft:bedrock" && event.block.typeId != "minecraft:frame" && event.block.typeId != "minecraft:glow_frame") {
        event.cancel = true;
        system.run(() => {
            const player = event.source
            player.sendMessage(`You cannot place Bedrock`)
        });
    }
});

world.beforeEvents.itemUseOn.subscribe(event => {
    if (event.itemStack.typeId === "minecraft:bedrock" && event.source.isSneaking === true) {
        event.cancel = true;
        system.run(() => {
            const player = event.source
            player.sendMessage(`You cannot place Bedrock`)
        });
    }
});

You can now modify the message sent to the player in player.sendMessage(). Put your message between the two backticks.

You can also change the typeId of the block in event.itemStack.typeId === "minecraft:bedrock". Put the namespace and identifier in place of minecraft:bedrock.

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