code: function interpolate(params) {
      const path = state.fullPath().replace(PARAMS, p => params[paramName(p)] || '')
  
      const queryParams = allQueryParams()
      const passedQueryParams = Object.keys(params).filter(p => queryParams[p])
  
      const query = passedQueryParams.map(p => p + '=' + params[p]).join('&')
  
      return path + (query.length ? ('?' + query) : '')
    }
docs: /*
  Returns a URI built from this state and the passed params.