I'm developing through Node. I have the following object in a Javascript file
function Person{
this.name = 'Peter',
this.lastname = 'Cesar',
this.age = 23
}
I want to instanciate this object in my Typescript code:
let peter: any = new Person();
But I'm getting "Cannot find name'Person' " it's normal because I need to define the signature for the function before. How can I achieve this ?
The answer is a mix of @TomKunzemann and @GauravSrivastava's answers: You should declare it as a class.
With declare you are just telling the compiler about the shape and behavior of the type without implementing it, so it relies on an ambient Person function being included with your JavaScript.
And with class, you are telling TypeScript that it's the sort of thing that you instantiate with new.
Finally, you probably don't want to define peter be of type any, or TypeScript will not type check it afterwards. If you just leave off the : any, TypeScript will infer peter to be of type Person and it will perform the desired type checks, such as detecting typos (e.g., lastName instead of lastname):
declare class Person {
name: string;
lastname: string;
age: number;
}
let peter = new Person(); // okay
console.log(peter.name); // okay
// note the typo below
console.log(peter.lastName); // error!
// "Property 'lastName' does not exist on type 'Person'. Did you mean 'lastname'"?
Hope that helps; good luck!
So first I think your vanilla javascript syntax is wrong, should be
function Person() {
this.name = 'Peter';
this.lastname = 'Cesar';
this.age = 23;
}
Then in typescript you can do
declare var Person: any;
let peter: any = new Person;
let john: any = new Person;
Ensure the external js is included then you can have multiple objects of Person
Use this instead of Person function:
export class Person {
name:string = 'Peter';
lastname:string = 'Cesar';
age:number = 23
}
Yeah I think what you need to do is to "declare" the function.
declare function Person(): void;
You can read about "declare" in the official documentation.
