This is the documentation of version 0.62.2. Go to the latest version, 1.0.0-rc.5.
TomTom Maps for JavaScript
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    Type Alias FeaturePropValue

    FeaturePropValue:
        | string
        | number
        | boolean
        | null
        | undefined
        | FeaturePropValue[]
        | { [key: string]: FeaturePropValue }

    A value a GeoJSON feature property can hold.