Minecraft wiki entry for Development_versions, associated text: Mob events can now be enabled and disabled in world templates.
Animations and particles can be added without being linked to entities.
Inventory, armor, and hand containers can be adapted through scripting.
Sound effects can now be triggered by animation events.
Added new executeCommand to the Scripting API.
Added Scripting events for interaction with items, for example:
Item picked up
Item dropped
Carried item changed
Added One-shot animation support, allowing the ability to execute a single animation on an entity.
Particle emitters can now trigger scripting events.
Updated documentation of actor events, to document client-side usage of actor events in resource packs.
"Add block" components now use JSON schemas.
Added a screen to view content log errors.
The log screen can be opened using Ctrl+H, or by going to Settings and then Profile.
Added code to allow static validation scripts to be run locally.
Custom blocks can now be added through Scripting.
This is currently still a "work in progress" feature, and more functionality will be added in future updates.
Custom blocks can currently only be added through additional JSON scripting.
Custom blocks can only be placed with slash commands.
Added new data-driven particles:
Llama Spit
Large Explosions
Colored Flames
Redstone Dust
Falling Dust
Lava
Enchanting Table
Conduit
Added new data-driven animations:
Wolves
Fang Attack
Arrows
Shulker Bullets
Bows
Water
Updated documentation to include a breaking changes section.
Basic item related events have been exposed to the scripting API. This includes:
actor_acquired_item
actor_carried_item_changed
actor_dropped_item
actor_use_item
actor_equipped_armor
Basic inventory events have been exposed to the scripting API. This includes:
inventory_container
armor_container
hand_container
hotbar_container
New block events and two new APIs have been included to query for blocks. This includes:
APIs
getBlock(Ticking Area, x, y, z)
getBlock(Ticking Area, PositionObject)
getBlocks(Ticking Area, x min, y min, z min, x max, y max, z max)
getBlocks(Ticking Area, Minimum PositionObject, Maximum PositionObject)
Events:
block_destruction_started
block_destruction_stopped
piston_moved_block
player_destroyed_block
player_placed_block
executeCommand API
Allows the scripting API to get the result of a slash command.
Event data API:
Allows creators to create event data, register and pass it to the event function.
Updated demo pack.
Biome generation is now customizable via behavior packs.