What is an object initializer?

0-2 years experience

1. 1How would you create a new user object with `name` and `email` properties using an object initializer?
2. 2Given variables `firstName` and `lastName`, show how to build an object that automatically uses those variable names as property keys.
3. 3What will the object look like after executing `const obj = {a: 1, a: 2};` and why?

2-5 years experience

1. 1You need to merge default settings with a response from an API. Walk me through how you'd use an object initializer and spread syntax to build the final config, and what pitfalls you’d watch for.
2. 2A teammate added a new field to a request payload, but the server receives `undefined`. The code uses a computed property name inside an object initializer. How would you debug the issue?
3. 3Explain why spreading an object into another initializer (`{...base, id: 5}`) can unintentionally overwrite properties, and how you'd guard against that in a larger codebase.

5-8 years experience

1. 1Our front‑end team shares a UI theme object built from several modules. How would you design its initialization to ensure immutability and avoid circular references when the app scales?
2. 2When serializing objects for storage we need to strip functions and prototype methods. Show how you'd use an object initializer to create a plain data snapshot, and discuss performance considerations for millions of records.
3. 3We are refactoring a legacy codebase that constructs objects via constructor functions. What are the trade‑offs of converting those to plain object initializers, especially regarding prototype inheritance and memory usage?

8+ years experience

1. 1Our organization is moving from a monolithic config file to a distributed, version‑controlled configuration service. How would you redesign component configuration creation using object initializers to support lazy loading and backward compatibility?
2. 2Across several microservices we need a consistent shape for request payloads. Describe how you'd establish a shared library that defines these shapes with object initializers, and how you'd evolve them without breaking existing services.
3. 3When migrating a large codebase to TypeScript, how would you leverage object initializer patterns to enforce type safety while minimizing churn, and what architectural guidelines would you set for future developers?