When I first started learning TypeScript, I encountered an issue that has me stuck.
In my code, there are two versions: in the first version, there is an object called name, and in the second version (which is essentially the same), the variable name has been changed to user. The problem is that the first version is throwing an error, while the second version is running smoothly.
Error-producing First Code
interface Person {
firstName : string;
lastName : string;
}
function greeter(person: Person) {
return "Hello " + person.firstName + " " + person.lastName;
}
var name = {firstName: "Girdhari", lastName: "Agrawal"};
document.body.innerHTML = greeter(name);
Working Fine Second Code
interface Person {
firstName : string;
lastName : string;
}
function greeter(person: Person) {
return "Hello " + person.firstName + " " + person.lastName;
}
var user = {firstName: "Girdhari", lastName: "Agrawal"};
document.body.innerHTML = greeter(user);
I'm struggling to understand this difference between the two versions. Any help would be appreciated.
Edit:
Upon compiling the first script, I received the following errors:
greeter.ts(10,5): error TS2403: Subsequent variable declarations must have the same type. Variable 'name' must be of type 'string', but here has type '{ firstname: string; lastName: string; }'.
greeter.ts(13,35): error TS2345: Argument of type 'string' is not assignable to parameter of type 'Person'.