پردازش پس‌زمینه‌ای کارآمد

.heavy-component {
  /* Defer rendering work when off-screen */
  content-visibility: auto;
  
  /* Mandatory: Provide a placeholder size to prevent layouts shifts.
    - 'auto' is optional and enables the browser to remember the actual size
      once rendered. It must be paired with a <length> value to be used for
      the first render.
    - 'none' tells the browser not to apply any intrinsic width to this element.
      It can be used for either the height or the width value.
    - '500px' is the estimated height of this element. This can be any valid
      CSS <length> value. Replace it with the expected height of your
      component.
   */
  contain-intrinsic-size: auto none auto 500px;
}

const component = document.querySelector('.heavy-component');

// Option 1: Direct listener (recommended)
component.addEventListener('contentvisibilityautostatechange', (event) => {
  if (event.skipped) {
    // The browser skipped rendering this content.
    // DO NOT perform heavy mutations or animation loops here.
    stopSimulation();
    pauseWebSocketPolling();
  } else {
    // The browser is about to render the content.
    // Resume your work so it is ready when visible.
    startSimulation();
    resumeWebSocketPolling();
  }
});

// Option 2: Capturing listener for event delegation
document.addEventListener('contentvisibilityautostatechange', (event) => {
  if (event.target.matches('.heavy-component')) {
    if (event.skipped) {
      stopSimulation();
    } else {
      startSimulation();
    }
  }
}, { capture: true });

// Fallback using IntersectionObserver for older browsers
const target = document.getElementById('target-container');

// Check if content-visibility is supported
const isSupported = 'contentVisibility' in document.documentElement.style;

if (!isSupported) {
  const observer = new IntersectionObserver((entries) => {
    entries.forEach(entry => {
      if (entry.isIntersecting) {
        // The element is close to the screen. Start work!
        startSimulation();
      } else {
        // The element is far away. Pause work!
        stopSimulation();
      }
    });
  }, {
    // Use rootMargin to start rendering before it hits the screen
    rootMargin: '200px'
  });

  observer.observe(target);
}