frontend-api-integration-patterns

Frontend API Integration Patterns

Overview

This skill provides production-ready patterns for integrating frontend applications with backend APIs.

Most frontend issues are not caused by APIs being difficult to call, but by incorrect handling of asynchronous behavior—leading to race conditions, stale data, duplicated requests, and poor user experience.

This skill focuses on correctness, resilience, and user experience, not just making API calls work.

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When to Use This Skill

• Connecting frontend apps (React, React Native, Vue, etc.) to backend APIs
• Integrating ML/AI endpoints (/predict, /recommend)
• Handling asynchronous data in UI
• Fixing stale data, flickering UI, or duplicate requests
• Designing scalable frontend API layers

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Core Patterns

1. API Layer (Separation of Concerns)

Centralize API logic and normalize errors.

export class ApiError extends Error {
  constructor(message, status, payload = null) {
    super(message);
    this.name = "ApiError";
    this.status = status;
    this.payload = payload;
  }
}

export const apiClient = async (url, options = {}) => {
  const res = await fetch(url, {
    headers: { "Content-Type": "application/json" },
    ...options,
  });

  if (!res.ok) {
    let payload = null;
    try {
      payload = await res.json();
    } catch (_) {}

    throw new ApiError(
      payload?.message || "Request failed",
      res.status,
      payload
    );
  }

  // handle empty responses safely (e.g. 204 No Content)
  if (res.status === 204) return null;

  const text = await res.text();
  return text ? JSON.parse(text) : null;
};

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2. Race-Safe State Management

Prevent stale responses from overwriting fresh data.

useEffect(() => {
  let cancelled = false;

  const load = async () => {
    try {
      setLoading(true);
      setError(null);

      const result = await getUser();

      if (!cancelled) setData(result);
    } catch (err) {
      if (!cancelled) setError(err.message);
    } finally {
      if (!cancelled) setLoading(false);
    }
  };

  load();

  return () => {
    cancelled = true;
  };
}, []);