In this fragment I Have the next error :
Type 'string | null' is not assignable to type 'string'.
Type 'null' is not assignable to type 'string'. TS2322
export async function GetCertainCoinByType(coinId: string) {
const response = await axios.get(URLofCertainCoins + `certain/${coinId}`, {
headers : {
token : localStorage.getItem('token'),
}
});
return response;
}
That's because the return type of Local storage is string | null, and not just string. To avoid this exception, you can first get the item from local storage and then use it like:
export async function GetCertainCoinByType(coinId: string) {
let tokenFromStorage = localStorage.getItem('token')
if (!tokenFromStorage ) {
throw new Error("no token supplied");
}
const response = await axios.get(URLofCertainCoins + `certain/${coinId}`,
{
headers : {
token : tokenFromStorage
}
});
return response;
}
let, just put something like -> if (tokenFromStorage === null) { throw new Error("no token supplied"); } or something like that. This will then make TS happy.
getItem will cause the error again.. :( Using your original let, and doing the check after the let will fix that. That because getItem will always return string | null, but after doing a bounds check on the let it will become string..First, check whether token is null, and if it is, exit the function.
Now response is a Promise anyway, since it's returned by an async function. You don't need to await Axios, then re-convert it to a Promise afterwards. You can directly return axios.get(...) and since this removes the only await, it turns out you don't even need the async/await syntax at all here.
export function GetCertainCoinByType(coinId: string): Promise<any> {
const token:string|null = localStorage.getItem('token');
if(!token){
console.log("No token!");
return ;
}
return axios.get(URLofCertainCoins + `certain/${coinId}`, {
headers : { token }
});
}
token:string|null, implicit type is fine here. It's the bounds check that's important..