js 中添加click事件

<button onclick="alert('Hello World!')">Click Me</button>

document.getElementById('myButton').onclick = function() {
    alert('Hello World!');
};

document.getElementById('myButton').addEventListener('click', function() {
    alert('Hello World!');
});

window.onload = function() {
    var button = document.getElementById('myButton');
    if (button) {
        button.addEventListener('click', function() {
            alert('Hello World!');
        });
    } else {
        console.error('Element with ID "myButton" not found.');
    }
};

function handleClick() {
    alert('Hello World!');
}

var button = document.getElementById('myButton');
if (button.onclick !== handleClick) {
    button.removeEventListener('click', handleClick); // 先移除
    button.addEventListener('click', handleClick); // 再添加
}