js 图片 加载

const img = new Image();
img.src = 'path/to/image.jpg';
img.onerror = function() {
    console.error('图片加载失败');
};

function lazyLoad() {
    const images = document.querySelectorAll('img[data-src]');
    const options = {
        root: null,
        rootMargin: '0px',
        threshold: 0.1
    };
    const observer = new IntersectionObserver((entries, observer) => {
        entries.forEach(entry => {
            if (entry.isIntersecting) {
                const img = entry.target;
                img.src = img.dataset.src;
                observer.unobserve(img);
            }
        });
    }, options);
    images.forEach(img => observer.observe(img));
}

window.addEventListener('load', lazyLoad);

function preloadImages(sources, callback) {
    let loadedCount = 0;
    sources.forEach(src => {
        const img = new Image();
        img.src = src;
        img.onload = () => {
            loadedCount++;
            if (loadedCount === sources.length) {
                callback();
            }
        };
    });
}

preloadImages(['image1.jpg', 'image2.jpg'], () => {
    console.log('所有图片已预加载完成');
});