WorldgenAddEventJS

Example scripts:

onEvent('worldgen.add', event => {
  event.addLake(lake => {
    lake.block = 'minecraft:diamond_block'
    lake.chance = 3
  })

  event.addOre(ore => {
    ore.block = 'minecraft:glowstone'
    ore.spawnsIn.blacklist = false
    ore.spawnsIn.values = [
      '#minecraft:base_stone_overworld'
    ]
    
    ore.biomes.blacklist = true
    ore.biomes.values = [
      'minecraft:plains',
      '#nether'
    ]
    
    ore.clusterMinSize = 5
    ore.clusterMaxSize = 9
    ore.clusterCount = 30
    ore.minHeight = 0
    ore.maxHeight = 64
  })
  
  event.addSpawn(spawn => {
    spawn.category = 'creature'
    spawn.entity = 'minecraft:pig'
    spawn.weight = 10
    spawn.minCount = 4
    spawn.maxCount = 4
  })
})

All values are optional. All feature types have biomes field like addOre example

Valid biome categories (#category):

taiga

extreme_hills

jungle

mesa

plains

savanna

the_end

beach

forest

ocean

desert

river

swamp

mushroom

nether