src/State.js
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) : '')
  }
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) : '')
  }
/*
Returns a URI built from this state and the passed params.