js判断是否有img标签

if (document.getElementsByTagName('img').length > 0) {
    console.log('页面中存在img标签');
} else {
    console.log('页面中不存在img标签');
}

if (document.querySelectorAll('img').length > 0) {
    console.log('页面中存在img标签');
} else {
    console.log('页面中不存在img标签');
}

if (document.images.length > 0) {
    console.log('页面中存在img标签');
} else {
    console.log('页面中不存在img标签');
}

var container = document.getElementById('yourContainerId');
if (container.getElementsByTagName('img').length > 0) {
    console.log('容器中存在img标签');
} else {
    console.log('容器中不存在img标签');
}

document.addEventListener('DOMContentLoaded', function() {
    var observer = new MutationObserver(function(mutations) {
        mutations.forEach(function(mutation) {
            if (mutation.addedNodes.length) {
                mutation.addedNodes.forEach(function(node) {
                    if (node.tagName === 'IMG') {
                        console.log('动态添加了img标签');
                    }
                });
            }
        });
    });

    observer.observe(document.body, { childList: true, subtree: true });
});