Write a function `promiseRace(promises)` that resolves or rejects with the first settled promise.
Problem Statement
<p>Write a function <code>promiseRace(promises)</code> that resolves or rejects with the first settled promise.</p>
Examples
Input: promiseRace([slowPromise, fastPromise])
Output: Result of fastest promise
Explanation: Settles with the earliest settled promise.
Complexity
Time Complexity: O(N)
Space Complexity: O(N)
Hints
š” Hint 1:
Return a new Promise.
š” Hint 2:
The first promise to resolve or reject should settle the outer promise.
š” Hint 3:
promises.forEach(p => Promise.resolve(p).then(resolve, reject));
Editorial & Approach
Problem Overview & Intuition
To solve Promise.race Implementation, we consider the execution characteristics of JavaScript engines. Write a function `promiseRace(promises)` that resolves or rejects with the first settled promise. By utilizing idiomatic language constructs and clean algorithmic principles, we can accomplish this with optimal time and memory usage.
Step-by-Step Approach
- Understand Problem Contract: Identify input arguments, return type expectations, and edge cases (empty inputs, nullish values).
- Choose Core Mechanism: Use modern JavaScript patterns (return a new promise).
- Implement Logic: Handle state and transformations efficiently (the first promise to resolve or reject should settle the outer promise).
- Return Result: Ensure proper return format and preserve caller context if applicable.
Optimal Implementation (JavaScript)
function promiseRace(promises) {
return new Promise((resolve, reject) => {
promises.forEach(p => Promise.resolve(p).then(resolve, reject));
});
}Complexity Analysis
Time Complexity
O(N) parallel promise registration
Space Complexity
O(N) output buffer array
Edge Cases & Corner Traps Handled
- Empty or boundary inputs (empty arrays, strings, zero length).
- Type checks and unexpected values (e.g.
null,undefined, negative numbers). - Closure preservation and memory isolation between separate invocations.