Angular 5 is throwing an error (TS2678) because it is unable to compare the types 'String' and '""'

Here is the Angular 5 code snippet I have written:

gotToWallet(wallet) {

  const { countryId = '', currencyType = '' } = wallet || {};

  let walletIdentity;

  switch (currencyType) {
    case 'CRYPTO':
      walletIdentity = 'userWalletIdentity';
     break;
    case 'FIAT':
      walletIdentity = 'fiatWalletIdentity';
     break;
    case 'ERC20TOKEN':
      walletIdentity = 'xbxUserWalletIdentity';
     break;
 }

  const { currencyId = '' } = (wallet || {})[walletIdentity] || {};
  this.router.navigate([`walletMgmt/wallet-details/${currencyId}/${countryId}`]);

}

Upon running the ng build command, the following error occurs:

ERROR in src/app/wallet-management/wallets/wallets.component.ts(202,12): error TS2678: Type '"CRYPTO"' is not comparable to type '""'.
src/app/wallet-management/wallets/wallets.component.ts(205,12): error TS2678: Type '"FIAT"' is not comparable to type '""'.
src/app/wallet-management/wallets/wallets.component.ts(208,12): error TS2678: Type '"ERC20TOKEN"' is not comparable to type '""'.

I am puzzled by why this error is only appearing during the build process and not when using ng serve. Any guidance on resolving this issue would be greatly appreciated.

Thank you for your assistance.

javascripttypescriptswitch-statementangular5

Answer №1

if (currencyType === 'null') {

There seems to be an issue with the interpretation of currencyType: '' as type '""' instead of 'string' in the TypeScript version being used. Casting it as any should solve this problem.

Answer №2

The solution proposed by @QiaosenHuang is functional, but it goes against best practices for TypeScript by sacrificing type-safety, which is a core principle of TypeScript. The proper approach involves passing in a typed wallet using an interface.

interface IWallet {
  countryId: string;
  currencyType: string;
  // any other properties ...
}

function gotToWallet(wallet: IWallet) {
  // your code from the question ...
}

You mentioned testing for wallet || {}, leading to the use of a null coalescing operator for the function argument. However, your current code does not handle the scenario when wallet is undefined. A better solution would be to require wallet to adhere to the interface without the optional ? and perform the undefined check outside of this function.

Answer №3

Experiencing a similar issue recently, I discovered that the problem was caused by a cyclic import dependency in webpack.

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