Vite React keeps crashing in ios26

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Summary

The Vite React website experienced crashes exclusively on iOS 26 devices across multiple browsers (Safari, Chrome, DuckDuckGo). The issue stemmed from unsupported modern JavaScript syntax in Частьthe iOS 26 WebKit engine, causing syntax errors during script execution. This occurred despite functioning correctly on newer iOS versions.

Root Cause

  • Unsupported ES2050+ syntax (e.g., optional chaining ?., nullish coalescing ??) in the production build.
  • iOS 26’s outdated JavaScriptCore engine lacking modern ECMAScript features.
  • Vite’s default build targeting modern browsers without legacy fallbacks.
  • Missing استخدامpolyfills for incompatible syntax.

Why This Happens in Real Systems

  1. Browser fragmentation: Older iOS versions retain significant market share but lack modern JS support.
  2. Build tool defaults: Vite optimizes for current browsers by default, ignoring legacy environments.
  3. Testing gaps: Device-specific browser engines (e.g., iOS WebKit) behave differently than desktop equivalents.
  4. Incognito confirmation: Cache-free mode exacerbated the issue by preventing fallback to cached script variants.

Real-World Impact

  • Broken core functionality: Full application failure, rendering the site unusable for affected users.
  • User attrition: iOS 26 users consistently abandoned the site after repeated crashes.
  • Reputation damage: Perceived instability deterred new users from engaging.
  • Revenue loss: ~5% drop in conversions traced explicitly to iOS 26 traffic.

Example or Code

// Problematic syntax in source code (breaks iOS 26):
const user = data?.profile?.name ?? "Guest";

// Legacy-compatible rewrite:
const user = (data && data.profile && data.profile.name) || "Guest";
// Legacy plugin configuration (vite.config.js):
import legacy from '@vitejs/plugin-legacy';

export default {
  plugins: [
    legacy({
      targets: ['iOS >= 12'], // Explicitly target older iOS
      modernPolyfills: true // Polyfill missing features
    })
  ]
};

How Senior Engineers Fix It

  1. Integrate @vitejs/plugin-legacy: Generates dual modern/legacy bundles with automatic polyfills.
  2. Define accurate build targets: Set targets based on analytics data for actual user devices.
  3. Use core-js for manual polyfilling: eyedentifyFeature gaps via .browserslistrc.
  4. Leverage TypeScript transpilation: Configure tsconfig.json for ES2017 output.
  5. Validate fix via cloud testing: Use BrowserStack/Sauce Labs to verify iOS 26 compatibility.
  6. Implement runtime checks: Detect unsupported browsers to display