The mod that provide the json (maybe also js) API for Minecraft Modding.
All the definition json should go to the defs folder under your mod assets, the assets/modid/defs folders.
For Item, it goes items sub-folder: assets/modid/defs/items
For Block, it goes blocks sub-folder: assets/modid/defs/blocks
For Entity, it goes entities sub-folder: assets/modid/defs/entities
All the JSON contained by these 3 folders above, will be loaded into Minecraft.
All the JSON files in definition folder, should be a JSONArray looked like:
[{component-definition-a},{component-definition-b} ... ] Each component definition should have a property id which is unique to others.