Problem: Shape Legacy API Responses Without Touching the Source

med

30 min

Transform property names dynamically when accessing data from a legacy API object.

Problem statement

Your application consumes data from an old API that still uses inconsistent field names, such as fname and lname, instead of modern conventions like firstName and lastName.

You can’t modify the legacy source object directly because another system owns it, but you want the rest of your codebase to access it using consistent naming. You’ll use a Proxy to act as a translation layer—intercepting property reads and returning the correct value regardless of which version of the property name is used.

Goal

Create a function createApiAdapter(legacyObj) that returns a Proxy. The Proxy should map modern property names (firstName, lastName) to their legacy equivalents (fname, lname) transparently.

Constraints

You must use the get trap.
The original object must remain unchanged.
Unmapped properties should still return their normal values.
Access through either naming style (fname or firstName) should work.

Sample output

The examples below illustrate what the output should look like:

Problem: Shape Legacy API Responses Without Touching the Source

med

30 min

Transform property names dynamically when accessing data from a legacy API object.

Problem statement

Your application consumes data from an old API that still uses inconsistent field names, such as fname and lname, instead of modern conventions like firstName and lastName.

Goal

Constraints

You must use the get trap.
The original object must remain unchanged.
Unmapped properties should still return their normal values.
Access through either naming style (fname or firstName) should work.

Sample output

The examples below illustrate what the output should look like:

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Log Every Property Read on a Config Object

Node.js

// Legacy API object
const legacyUser = {
  fname: 'Alice',
  lname: 'Johnson',
  age: 30
};
// Your code here
// Example usage
const user = createApiAdapter(legacyUser);
console.log(user.firstName); // should return 'Alice'
console.log(user.lastName);  // should return 'Johnson'
console.log(user.age);       // should still return 30
/* Expected output:
Alice
Johnson
30
*/
// Accessing legacy fields directly should also still work
console.log(user.fname);     // 'Alice'
console.log(user.lname);     // 'Johnson'
/* Expected output:
Alice
Johnson
*/