tile-decorator 
A JavaScript module for decoding Mapbox vector tiles, doing various modifications in JS and reencoding back. It can:
- add and remove specific properties in a layer (
decorateLayer) - merge features with the same properties and type into one, and sort geometries within one feature by proximity for better compression (
mergeLayer) - get all values of a specific property in a layer (
getLayerValues) - rename layers (
layer.name = 'foo') - rename keys (
layer.keys[2] = 'kittens')