Lokalise SDK Patterns

Overview

Production-grade patterns for

@lokalise/node-api

Prerequisites

• @lokalise/node-api

  v12+ installed
• TypeScript 5+ with

  strict

  mode

Instructions

1. Create a client singleton to centralize configuration and support branch-based project IDs.

// src/lib/lokalise-client.ts
import { LokaliseApi } from "@lokalise/node-api";

let instance: LokaliseApi | null = null;

export function getClient(apiKey?: string): LokaliseApi {
  if (instance) return instance;
  const key = apiKey ?? process.env.LOKALISE_API_TOKEN;
  if (!key) throw new Error("Set LOKALISE_API_TOKEN or pass apiKey");
  instance = new LokaliseApi({ apiKey: key, enableCompression: true });
  return instance;
}

export function resetClient(): void { instance = null; }

/** Lokalise branch syntax: "projectId:branchName" */
export function projectId(id: string, branch?: string): string {
  return branch ? `${id}:${branch}` : id;
}

2. Build a cursor-based pagination helper that works with any paginated endpoint.

// src/lib/paginate.ts
interface PaginatedResult<T> {
  items: T[];
  hasNextCursor(): boolean;
  nextCursor(): string;
}

type Fetcher<T> = (params: Record<string, unknown>) => Promise<PaginatedResult<T>>;

/** Async generator yielding all items across pages with rate-limit spacing. */
export async function* paginate<T>(
  fetcher: Fetcher<T>,
  baseParams: Record<string, unknown>,
  pageSize = 500
): AsyncGenerator<T, void, undefined> {
  let cursor: string | undefined;
  let n = 0;
  do {
    const params = { ...baseParams, limit: pageSize, ...(cursor ? { cursor } : {}) };
    if (n++ > 0) await new Promise((r) => setTimeout(r, 170)); // 6 req/sec
    const page = await fetcher(params);
    for (const item of page.items) yield item;
    cursor = page.hasNextCursor() ? page.nextCursor() : undefined;
  } while (cursor);
}

/** Collect all pages into an array (use only when dataset fits in memory). */
export async function paginateAll<T>(fetcher: Fetcher<T>, params: Record<string, unknown>): Promise<T[]> {
  const out: T[] = [];
  for await (const item of paginate(fetcher, params)) out.push(item);
  return out;
}

Usage:

const allKeys = await paginateAll(
  (p) => client.keys().list(p),
  { project_id: "123456.abcdef", include_translations: 1 }
);

3. Wrap API calls with structured error handling that classifies retryable errors.

// src/lib/lokalise-api.ts
export class LokaliseError extends Error {
  constructor(
    message: string,
    public readonly statusCode: number,
    public readonly isRetryable: boolean
  ) {
    super(message);
    this.name = "LokaliseError";
  }
}

export async function apiCall<T>(fn: () => Promise<T>): Promise<T> {
  try {
    return await fn();
  } catch (err: unknown) {
    if (err && typeof err === "object" && "code" in err) {
      const e = err as { code: number; message: string };
      throw new LokaliseError(e.message, e.code, e.code === 429 || e.code >= 500);
    }
    throw err;
  }
}

// Usage
try {
  const keys = await apiCall(() => client.keys().list({ project_id: pid, limit: 500 }));
} catch (err) {
  if (err instanceof LokaliseError && err.isRetryable) {
    console.log("Transient failure, safe to retry");
  }
}

4. Batch key operations that chunk requests to respect the 500-key-per-request limit.

// src/lib/batch.ts
function chunk<T>(arr: T[], size: number): T[][] {
  const out: T[][] = [];
  for (let i = 0; i < arr.length; i += size) out.push(arr.slice(i, i + size));
  return out;
}

/** Create keys in batches of 500 with rate-limit spacing. */
export async function batchCreateKeys(
  client: LokaliseApi, projectId: string,
  keys: Array<{ key_name: { web: string }; platforms: string[]; tags?: string[];
    translations?: Array<{ language_iso: string; translation: string }> }>
): Promise<{ created: number; errors: Error[] }> {
  const batches = chunk(keys, 500);
  let created = 0;
  const errors: Error[] = [];
  for (let i = 0; i < batches.length; i++) {
    try {
      const r = await client.keys().create({ project_id: projectId, keys: batches[i] });
      created += r.items.length;
    } catch (err) { errors.push(err as Error); }
    if (i < batches.length - 1) await new Promise((r) => setTimeout(r, 500));
  }
  return { created, errors };
}

/** Delete keys in batches of 500. */
export async function batchDeleteKeys(
  client: LokaliseApi, projectId: string, keyIds: number[]
): Promise<number> {
  const batches = chunk(keyIds, 500);
  let deleted = 0;
  for (let i = 0; i < batches.length; i++) {
    const r = await client.keys().bulk_delete(batches[i], { project_id: projectId });
    deleted += r.keys_removed;
    if (i < batches.length - 1) await new Promise((r) => setTimeout(r, 500));
  }
  return deleted;
}

5. Upload files with async process monitoring and progress callbacks.

// src/lib/upload.ts
import { readFileSync } from "node:fs";

export async function uploadWithProgress(
  client: LokaliseApi, projectId: string,
  opts: { filePath: string; langIso: string; tags?: string[];
    replaceModified?: boolean; cleanupMode?: boolean },
  onProgress?: (status: string, elapsedMs: number) => void
): Promise<{ processId: string; status: string; durationMs: number }> {
  const data = readFileSync(opts.filePath).toString("base64");
  const start = Date.now();

  const proc = await client.files().upload(projectId, {
    data,
    filename: opts.filePath.split("/").pop()!,
    lang_iso: opts.langIso,
    replace_modified: opts.replaceModified ?? true,
    cleanup_mode: opts.cleanupMode ?? false,
    detect_icu_plurals: true,
    tags: opts.tags,
  });
  onProgress?.("queued", Date.now() - start);

  // Poll process status until terminal state
  const maxWait = 120_000; // 2 minutes
  let last = proc.status;
  while (Date.now() - start < maxWait) {
    await new Promise((r) => setTimeout(r, 1500));
    const check = await client.queuedProcesses().get(proc.process_id, { project_id: projectId });
    if (check.status !== last) { last = check.status; onProgress?.(last, Date.now() - start); }
    if (check.status === "finished") return { processId: proc.process_id, status: "finished", durationMs: Date.now() - start };
    if (check.status === "cancelled" || check.status === "failed") throw new Error(`Upload ${check.status}: ${JSON.stringify(check.details)}`);
  }
  throw new Error(`Upload timed out after ${maxWait}ms`);
}

Usage:

await uploadWithProgress(client, "123456.abcdef", {
  filePath: "./src/locales/en.json",
  langIso: "en",
  tags: ["ci"],
  replaceModified: true,
}, (status, ms) => console.log(`[${(ms / 1000).toFixed(1)}s] ${status}`));

6. Add a retry decorator with exponential backoff and a rate limiter for sequential calls.

// src/lib/retry.ts
/** Retry on 429 and 5xx with exponential backoff + jitter. */
export async function withRetry<T>(
  fn: () => Promise<T>,
  opts: { maxRetries?: number; baseDelayMs?: number; maxDelayMs?: number;
    onRetry?: (attempt: number, err: Error, delayMs: number) => void } = {}
): Promise<T> {
  const { maxRetries = 3, baseDelayMs = 1000, maxDelayMs = 10_000, onRetry } = opts;
  let lastErr: Error | undefined;
  for (let i = 0; i <= maxRetries; i++) {
    try { return await fn(); }
    catch (err: unknown) {
      lastErr = err as Error;
      const code = (err as { code?: number })?.code;
      if (!(code === 429 || (code && code >= 500)) || i === maxRetries) throw err;
      const delay = Math.min(baseDelayMs * 2 ** i + Math.random() * 200, maxDelayMs);
      onRetry?.(i + 1, lastErr, delay);
      await new Promise((r) => setTimeout(r, delay));
    }
  }
  throw lastErr;
}

/** Enforce minimum spacing between calls (default: 170ms = 6 req/sec). */
export function rateLimited<A extends unknown[], R>(
  fn: (...args: A) => Promise<R>, minMs = 170
): (...args: A) => Promise<R> {
  let last = 0;
  return async (...args) => {
    const wait = minMs - (Date.now() - last);
    if (wait > 0) await new Promise((r) => setTimeout(r, wait));
    last = Date.now();
    return fn(...args);
  };
}

Usage:

// Single call with retry
const keys = await withRetry(
  () => client.keys().list({ project_id: pid, limit: 500 }),
  { onRetry: (n, e, ms) => console.warn(`Retry ${n}: ${e.message} (${ms}ms)`) }
);

// Rate-limited sequential calls
const listKeys = rateLimited((p: Record<string, unknown>) => client.keys().list(p));
const p1 = await listKeys({ project_id: pid, page: 1, limit: 100 });
const p2 = await listKeys({ project_id: pid, page: 2, limit: 100 });

Output

• Singleton client with compression and branch support
• Async generator for memory-efficient cursor pagination
• Type-safe error wrapper with

  isRetryable

  classification
• Batch create/delete respecting 500-key API limit
• File upload with process polling and progress callbacks
• Retry with exponential backoff + rate limiter at 6 req/sec

Error Handling

apiCall()

LokaliseError

isRetryable

withRetry()

rateLimited()

paginate()

batchCreateKeys()

uploadWithProgress()

Examples

Combining All Patterns

import { getClient, projectId } from "./lib/lokalise-client";
import { paginateAll } from "./lib/paginate";
import { withRetry } from "./lib/retry";
import { batchCreateKeys } from "./lib/batch";
import { uploadWithProgress } from "./lib/upload";

const client = getClient();
const pid = projectId("123456.abcdef", "develop");

// Upload, paginate, batch create, download — all with rate limiting and retry
await uploadWithProgress(client, pid, { filePath: "./src/locales/en.json", langIso: "en" },
  (s, ms) => console.log(`[${ms}ms] ${s}`));

const allKeys = await paginateAll((p) => client.keys().list(p), { project_id: pid });
console.log(`${allKeys.length} keys`);

const result = await batchCreateKeys(client, pid,
  Array.from({ length: 1200 }, (_, i) => ({
    key_name: { web: `gen.key_${i}` }, platforms: ["web"],
    translations: [{ language_iso: "en", translation: `Val ${i}` }],
  })));
console.log(`Created ${result.created}, errors: ${result.errors.length}`);

const bundle = await withRetry(() => client.files().download(pid, {
  format: "json", original_filenames: false, bundle_structure: "%LANG_ISO%.json",
}));
console.log(`Download: ${bundle.bundle_url}`);

Resources

• Node SDK Documentation
• Pagination Guide
• API Rate Limits
• API Error Codes
• Branching

Next Steps

Apply these patterns in

lokalise-core-workflow-a

lokalise-core-workflow-b