promoteId

A property to use as a feature id (for feature state). It can be a property name, or an expression to evaluate as the ID, or an object of the form {<sourceLayer>: <propertyName/expression>}. The expression can only be feature dependent if it is used. If specified as a string for a vector tile source, the same property is used across all its source layers. If specified as an object only specified source layers will have id overriden, others will fallback to original feature id