Given is the following function prototype:
function get(): string { /*.../* }
Can this function return null or undefined? Or only one of them? I try to understand which checks I should apply to check for validty of the return type of the function
It depends on your compilerOptions. The strictNullChecks flag, to be precise.
strictNullChecks: false
function get(): string {
return null; // ok
}
function get(): string {
return undefined; // ok
}
In this scenario, you need extra checks against null and undefined.
strictNullChecks: true
The return value must be of type string. null and undefined are not allowed. No extra checks are necessary.
function get(): string {
return null; // Compile-time error
}
function get(): string {
return undefined; // Compile-time error
}
Check your tsconfig.json and set compilerOptions.strictNullChecks the way you prefer.
No, This function must only return string.
If you want you have to set other type:
function get(): string | undefined | null {/*....*/ }
Or if you want to return only string you must check extra conditions.
