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/** |
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* Optimole LCP (Largest Contentful Paint) Detection Module |
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* Handles LCP element detection and processing |
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*/ |
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|
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import { optmlLogger } from './logger.js'; |
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import { optmlDomUtils } from './dom-utils.js'; |
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|
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/** |
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* LCP detection utilities |
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*/ |
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export const optmlLcp = { |
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/** |
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* Detect and process LCP element |
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* @returns {Promise<Object>} Promise that resolves with LCP data |
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*/ |
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detectLcpElement: async function() { |
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// Track LCP element - use a single object to store all LCP data |
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const lcpData = { |
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element: null, |
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imageId: null, |
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bgSelector: null, |
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bgUrls: null |
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}; |
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|
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// Set up LCP detection - more performant approach |
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if (!PerformanceObserver.supportedEntryTypes.includes('largest-contentful-paint')) { |
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optmlLogger.info('LCP detection not supported in this browser'); |
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return lcpData; |
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} |
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|
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// Use a pre-existing LCP entry if available instead of waiting |
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const lcpEntries = performance.getEntriesByType('largest-contentful-paint'); |
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|
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if (lcpEntries && lcpEntries.length > 0) { |
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// Use the most recent LCP entry |
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const lastEntry = lcpEntries[lcpEntries.length - 1]; |
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if (lastEntry && lastEntry.element) { |
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lcpData.element = lastEntry.element; |
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optmlLogger.info('LCP element found from existing entries:', lcpData.element); |
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this._processLcpElement(lastEntry.element, lcpData); |
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} |
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} else { |
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// If no existing entries, set up observer with shorter timeout |
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optmlLogger.info('Setting up LCP observer'); |
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|
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// Create a promise that will resolve when LCP is detected or timeout |
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await new Promise(resolve => { |
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const lcpObserver = new PerformanceObserver(entryList => { |
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const entries = entryList.getEntries(); |
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if (entries.length === 0) return; |
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|
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// Use the most recent entry |
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const lastEntry = entries[entries.length - 1]; |
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if (lastEntry && lastEntry.element) { |
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lcpData.element = lastEntry.element; |
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optmlLogger.info('LCP element detected:', lcpData.element); |
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this._processLcpElement(lastEntry.element, lcpData); |
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} |
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|
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lcpObserver.disconnect(); |
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resolve(); |
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}); |
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|
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lcpObserver.observe({ type: 'largest-contentful-paint', buffered: true }); |
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|
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// Use a shorter timeout - most LCP elements are detected within 1-2 seconds |
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setTimeout(() => { |
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lcpObserver.disconnect(); |
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resolve(); |
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}, 1500); |
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}); |
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} |
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|
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return lcpData; |
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}, |
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|
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/** |
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* Process LCP element to extract relevant data |
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* @private |
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* @param {Element} element - LCP element |
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* @param {Object} lcpData - LCP data object to populate |
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*/ |
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_processLcpElement: function(element, lcpData) { |
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if (!element) return; |
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|
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// Check if LCP element is an image with data-opt-id |
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if (element.tagName === 'IMG') { |
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const id = element.getAttribute('data-opt-id'); |
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if (id) { |
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lcpData.imageId = parseInt(id, 10); |
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optmlLogger.info('LCP element is an Optimole image with ID:', lcpData.imageId); |
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} |
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} |
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// Check if LCP element has a background image |
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else { |
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const bgImage = optmlDomUtils.hasBackgroundImage(element, true); |
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|
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if (bgImage !== false) { |
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lcpData.bgSelector = optmlDomUtils.getUniqueSelector(element); |
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lcpData.bgUrls = optmlDomUtils.extractUrlsFromBgImage(bgImage); |
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|
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optmlLogger.info('LCP element has background image:', lcpData.bgSelector, lcpData.bgUrls); |
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} |
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} |
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} |
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}; |
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