fakeFetch.js

function testCall(a) {
   fakeFetch(a)
    .then((response) => {
      if (a === 'works' && typeof response.data !== 'object') {
        setState(fallbackRes)
        return          
      }

      if (typeof response.data === 'object') {
        setState(response.data)
        return
      }

      testCall('works')
      
    })
}

unzip.ts

/**
 * Unzip Tuple
 * [ [1,a], [2,b] ] ==> [1, a, 2, b]
 * @param {array} zipped tuple
 * @returns {array} flated array
 */
function unzip(tuple: Array<[number, string]>) {

 if (!tuple || Array.isArray(tuple)) {
   return false 
 }

 return [].concat(...tuple)

}