Overall Goal:

• Object se sirf specific keys pick karna.
• New object banana (original mutate nahi karna).

Solution:

• const pick = (obj, keys) => keys.reduce((acc, k) => (k in obj ? ((acc[k] = obj[k]), acc) : acc), {});

Part 1: Function header

• const pick = (obj, keys) => → function jo object aur keys array lega.

Part 2: Reduce logic

• keys.reduce((acc, k) => ..., {})
• reduce → keys array ko traverse karke single object banana.
• {} → initial value (empty object).

Part 3: Key check and copy

• (k in obj ? ((acc[k] = obj[k]), acc) : acc)
• k in obj → kya key object me exist karti hai?
• Agar hai:
• acc[k] = obj[k] → key-value copy karo.
• , acc → comma operator: last expression acc return.
• Agar nahi: acc as-is return (key skip).

Example:

• pick({a: 1, b: 2, c: 3}, ["a", "c"]) → {a: 1, c: 3}.

Real world:

• API payload sanitize: sirf required fields send karna.
• Form data: selected fields extract karna.
• Data transformation: object subset banana.