Property id does not exist on type string

Question

I am getting the follow error in my IDE saying Property id does not exist on type string typeScript for this line of code:

if(customer.id === id) {//doesn't like customer.id
            return customer;
        }

full code:

let customer:any [];

function Customers(): string[] {

    let id = 0;

    createCustomer("Drew",id++,22,"Glassboro");
    createCustomer("Mike",id++,40,"Rineyville");
    createCustomer("Justin",id++,19,"Jonesboro");
    createCustomer("Alex",id++,15,"Paulsboro");
    createCustomer("Phil",id++,32,"Glassboro");

    return customer;
}

function createCustomer(name:string,id:number,age:number,city:string){
        customer.push(name,id,age,city);
}

const allCustomers = Customers();

function getCustomerInformation(id:number): string {

    for (let customer of allCustomers) {

        if(customer.id === id){
            return customer;
        }

    }

    return "";
}

It was my assumption since I used any for let customer:any []; I could put different variables in there.

----------------- Thanks for some help this is my new solution--------

interface ICustomer{
    id: number;
    name: string;
    age: number
    city: string
}

let customers: Array<ICustomer>;

function generateCustomers(): void {

    let id: number = 0;

    createCustomer("Drew", id++, 22, "Glassboro");
    createCustomer("Mike", id++, 40, "Rineyville");
    createCustomer("Justin", id++, 19, "Jonesboro");
    createCustomer("Alex", id++, 15, "Paulsboro");
    createCustomer("Phil", id++, 32, "Glassboro");

}

function getAllCustomers(): ICustomer[]{

    generateCustomers();

    return customers;
}

function createCustomer(name:string,id:number,age:number,city:string): void {

    let newCustomer:ICustomer = {id:id,name:name,age:age,city:city};

    customers.push(newCustomer);
}

const allCustomers = getAllCustomers;

function getCustomerInformation(id:number): ICustomer {

    for (let customer of allCustomers()) {

        if(customer.id === id){
            return customer;
        }
    }

    return null;
}


console.log(getCustomerInformation(1));

Answer 1

You have to wrap your properties inside of object:

function createCustomer(name: string, id: number, age: number, city: string) {
        customer.push({ name, id, age, city });
}

Where { name, id, age, city } is ES2015 equivalence of:

{
    id: id,
    name: name,
    age: age,
    city: city
}

To avoid this kind of mistakes, I tend to create interface that forces structure:

interface ICustomer {
    id: number;
    name: string;
    age: number;
    city: string;
}

which you assign to your array:

let customer: ICustomer[];

Except better type checking, it gives you better syntax hints.

---

Edit: I've reviewed your code and made few suggestions about practices:

• Always give return type to functions
• Try to not work on external variables inside functions, if needed pass them as parameters
• Don't mix function definitions with actual code

Code worth more than 1000 words. Here is refactored version:

const allCustomers: ICustomer[] = customers();

interface ICustomer {
    id: number;
    name: string;
    age: number;
    city: string;
}

function customers(): ICustomer[] {
    let id: number = 0;

    return [
        createCustomer(id++, "Drew", 22, "Glassboro"),
        createCustomer(id++, "Mike", 40, "Rineyville"),
        createCustomer(id++, "Justin", 19, "Jonesboro"),
        createCustomer(id++, "Alex", 15, "Paulsboro"),
        createCustomer(id++, "Phil", 32, "Glassboro")
    ];
}

function createCustomer(id: number, name: string, age: number, city: string): ICustomer {
    return { id, name, age, city };
}

function getCustomerInformation(customers: ICustomer[], id: number): ICustomer {
    // Note undefined is returned if object not found
    return customers.find(customer => customer.id === id);
}