Managing updates with the spread syntax: Dealing with undefined or null properties

Question

Managing updates with the spread syntax: Dealing with undefined or null properties

Let's take a look at this example method:


GetCustomerWithPoints(customerId: number): Customer {
  const customer = this.customerService.getCustomer(customerId);
  const points = this.pointService.getPointsForCustomer(customerId);

   return {...customer, [customer.rewards.points]: points };
}

What should we do when customer.rewards is either null or undefined? Should the points only be set if the rewards object actually exists?

An issue I'm encountering with this code is the error message saying Object is possibly 'undefined'.

typescript ecmascript-6

Answer 1

Answer №1

To ensure safety, always verify the actual value before accessing it in your code. Here's a method to do so:

ProcessCustomer(customerId: number): UpdatedCustomer {
  const customer = this.customerService.fetchCustomer(customerId);
  const points = this.pointService.retrievePointsForCustomer(customerId);

  if(!customer.pointsAccumulated) {
    // If points are not defined, return the customer as is
    return customer;
  }
  
  // If points exist, include them in the updated customer object:
  return {...customer, [customer.pointsAccumulated]: points};
}

Alternatively, you can use a more concise approach:

ProcessCustomer(customerId: number): UpdatedCustomer {
  const customer = this.customerService.fetchCustomer(customerId);
  const points = this.pointService.retrievePointsForCustomer(customerId);

  return {
    ...customer,
    ...(customer.pointsAccumulated ? { [customer.pointsAccumulated]: points } : {})
  };
}

Answer 2

To ensure safety, always verify the actual value before accessing it in your code. Here's a method to do so:

ProcessCustomer(customerId: number): UpdatedCustomer {
  const customer = this.customerService.fetchCustomer(customerId);
  const points = this.pointService.retrievePointsForCustomer(customerId);

  if(!customer.pointsAccumulated) {
    // If points are not defined, return the customer as is
    return customer;
  }
  
  // If points exist, include them in the updated customer object:
  return {...customer, [customer.pointsAccumulated]: points};
}

Alternatively, you can use a more concise approach:

ProcessCustomer(customerId: number): UpdatedCustomer {
  const customer = this.customerService.fetchCustomer(customerId);
  const points = this.pointService.retrievePointsForCustomer(customerId);

  return {
    ...customer,
    ...(customer.pointsAccumulated ? { [customer.pointsAccumulated]: points } : {})
  };
}

Managing updates with the spread syntax: Dealing with undefined or null properties

Answer №1

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