无法获取动态document.getElementById值

// HTML
<div id="container">
    <!-- 动态生成的元素 -->
    <button id="dynamicBtn">点击我</button>
</div>

// JavaScript
var container = document.getElementById('container');
container.addEventListener('click', function(event) {
    if (event.target.id === 'dynamicBtn') {
        var value = event.target.value;
        // 处理获取到的值
    }
});

// HTML
<div>
    <!-- 动态生成的元素 -->
    <button id="dynamicBtn">点击我</button>
</div>

// JavaScript
(function() {
    var dynamicBtn = document.getElementById('dynamicBtn');
    var value = "动态生成元素的值";
    dynamicBtn.addEventListener('click', function() {
        // 处理获取到的值
        console.log(value);
    });
})();

// HTML
<div id="container"></div>

// JavaScript
var container = document.getElementById('container');
var observer = new MutationObserver(function(mutationsList) {
    for (var mutation of mutationsList) {
        if (mutation.type === 'childList' && mutation.addedNodes.length) {
            var dynamicBtn = mutation.addedNodes[0];
            var value = dynamicBtn.value;
            // 处理获取到的值
        }
    }
});
observer.observe(container, { childList: true });