Unhandled Rejection (TypeError): Invalid attempt to spread non-iterable instance how can I fix

Question

I am having error like this in my project:

Unhandled Rejection (TypeError): Invalid attempt to spread non-iterable instance. In order to be iterable, non-array objects must have a Symbol.iterator method

Here is my SortContracts.ts code:

function sortContracts(
  contracts: ContractUsage[],
  sortField?: SortType,
  sortDirection?: SortDirection
): any[] {
  let sortFunction:any
  switch (sortField) {
    // Sort by End Date
    case SortType.DATE_SORT:
      if (sortDirection === SortDirection.ASC) {
        // Sort by End Date ASC
        sortFunction = (a:any, b:any) => endDateSortAscFunc(a, b);
      } else {
        // Sort by End Date DESC
        sortFunction = (a:any, b:any) => endDateSortDescFunc(a, b);
      }
      break;

    // Sort by ContractID
    case SortType.CONTRACT_SORT:
      if (sortDirection === SortDirection.ASC) {
        // Sort by ContractID ASC
        sortFunction = (a:any, b:any) => contractIdSortAscFunc(a, b);
      } else {
        // Sort by ContractID DESC
        sortFunction = (a:any, b:any) => contractIdSortDescFunc(a, b);
      }
      break;

    case SortType.USAGE_ORDER:
      if (sortDirection === SortDirection.ASC) {
        sortFunction = (a:any, b:any) => usageOrderSortAscFunc(a, b);
      } else {
        sortFunction = (a:any, b:any) => usageOrderSortDescFunc(a, b);
      }
      break;
    // default sort
    default:
      sortFunction = (a:any, b:any) => contractIdSortAscFunc(a, b);
  }

  // Return the sorted contracts
  console.log('contract here: ',  [...contracts].sort(sortFunction))
  return [...contracts].sort(sortFunction);
}

Answer 1

The variable you are trying to spread (ie. [...contracts] ) is not iterable . If you want use this operator, you need to have this variable iterable . Check the variable if it is really an array (or any other iterable type) and if it's not null or undefined .