How to create an associative array in typescript with a property that iterates the associative array itself

Question

I'm trying to create an object, that works like an array and could have some properties that could iterate the same array:

interface ICustomer {
  orderId: string
  name: string
}

interface ICustomers {
  [key: number]: ICustomer
  findByOrderId: (id:string) => ICustomer
}

Now trying to create an example instance of ICustomers:

const customers: ICustomers = {
  0: {
    orderId: 'aaa',
    name: "Johny"
  },
  1: {
    orderId: 'bbb',
    name: "Pablo"
  },

  findByOrderId: function(id: string) {
    for (customer of this) {
      if (customer.orderId === id) {
        return customer
      }
    }

    return null
  }
}

It shows the following error: Type 'ICustomers' must have a '[Symbol.iterator]()' method that returns an iterator.(2488)

How to implement 'Symbol.iterator' in this case? Maybe there is another approach?

Here is a demo

basarat · Accepted Answer · 2020-06-10 03:40:10Z

1

Error

In order to use for of you need to provide [Symbol.iterator]

Fix

Add that to the interface and the implementation. Code without any errors:

interface ICustomer {
  orderId: string
  name: string
}

interface ICustomers {
  [key: number]: ICustomer
  [Symbol.iterator]: () => Generator<ICustomer>
  findByOrderId: (id: string) => ICustomer | null
}

const customers: ICustomers = {
  0: {
    orderId: 'aaa',
    name: "Johny"
  },
  1: {
    orderId: 'bbb',
    name: "Pablo"
  },

  [Symbol.iterator]: function* () {
    yield this[0];
    yield this[1];
  },

  findByOrderId: function (id: string) {
    for (let customer of this) {
      if (customer.orderId === id) {
        return customer
      }
    }

    return null
  }
}

answered Jun 10, 2020 at 3:40

basarat

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