Promise.all() for Independent Operations
Install this skill
npx skills add vercel-labs/agent-skillsWorks across Claude Code, Cursor, Codex, Copilot & Antigravity
This pattern reduces latency in asynchronous JavaScript operations by executing independent tasks concurrently rather than waiting for each to finish before starting the next. By grouping promises into a single array passed to Promise.all(), the runtime initiates all network requests or file system operations simultaneously. This approach optimizes the total wait time to match the duration of the slowest individual task rather than the sum of all tasks. This technique is essential for performance-sensitive applications where multiple data sources must be fetched before rendering or processing can begin. It prevents the sequential blocking behavior inherent in repeated await statements, ensuring the event loop remains responsive and overall execution time is minimized without adding unnecessary complexity to the codebase.
When to Use This Skill
- •Fetching profile data, activity logs, and notification counts simultaneously on page load
- •Loading configuration files from different remote endpoints
- •Processing multiple separate database queries that do not rely on each other's output
- •Running independent validation checks across distinct data services
How to Invoke This Skill
Example prompts that trigger this skill in Claude Code, Cursor, or Antigravity:
- “Run these async tasks at the same time
- “Make my API calls parallel to save time
- “Stop waiting for each fetch to finish individually
- “Execute multiple promises concurrently
- “Optimize sequential await statements
What this skill does
- •Groups multiple independent asynchronous promises into a single execution unit
- •Aggregates result values into a single array matching input order
- •Minimizes total latency to the duration of the longest request
- •Provides a unified interface for handling concurrent I/O operations
- •Enables immediate rejection if any single promise within the array fails
When not to use it
- ✕When subsequent operations depend on the result of a previous promise
- ✕When you need to handle partial failures or continue even if one request errors
Example workflow
- Identify independent async functions that do not share state
- Map these functions into an array structure
- Pass the array into the Promise.all constructor
- Apply await to the entire Promise.all expression
- Destructure the returned array to access specific results
Prerequisites
- –Familiarity with JavaScript async/await syntax
- –Understanding of the event loop
Pitfalls & limitations
- !Fails fast; one rejection causes the entire operation to reject immediately
- !Does not inherently throttle the number of concurrent connections
- !Requires careful error handling if partial success is desired
FAQ
How it compares
While manual sequencing blocks the thread unnecessarily for each task, Promise.all orchestrates parallel execution to collapse multiple round-trips into one.
📄 Full skill instructions — original source: vercel-labs/agent-skills
When async operations have no interdependencies, execute them concurrently using
Promise.all().**Incorrect (sequential execution, 3 round trips):**
const user = await fetchUser()
const posts = await fetchPosts()
const comments = await fetchComments()**Correct (parallel execution, 1 round trip):**
const [user, posts, comments] = await Promise.all([
fetchUser(),
fetchPosts(),
fetchComments()
])How to Use This Skill Unit
Option A: Project-Specific (Recommended)
- Click "Download" above
- In your project, create the directory:
.agent/skills/async-parallel/ - Save the file as
SKILL.md - The agent will automatically discover the skill based on its description.
Option B: Global Installation (All Agents)
Save the file to these locations to make it available across all projects:
- Claude Code:
~/.claude/skills/vercel-labs/agent-skills/async-parallel/SKILL.md - Cursor:
~/.cursor/skills/vercel-labs/agent-skills/async-parallel/SKILL.md - Antigravity:
~/.gemini/antigravity/skills/vercel-labs/agent-skills/async-parallel/SKILL.md
🚀 Install with CLI:npx skills add vercel-labs/agent-skills