如何修复Javascript的onclick调用？

<button onclick="undefinedFunction()">Click Me</button>

<script>
function definedFunction() {
    alert('Function called!');
}
</script>
<button onclick="definedFunction()">Click Me</button>

<script>
(function() {
    function scopedFunction() {
        alert('Scoped function called!');
    }
})();
</script>
<button onclick="scopedFunction()">Click Me</button>

<script>
window.scopedFunction = function() {
    alert('Scoped function called!');
};
</script>
<button onclick="scopedFunction()">Click Me</button>

<button onclick="alert('Hello, world!';)">Click Me</button>

<button onclick="alert('Hello, world!');">Click Me</button>

<button onclick="fetchData()">Click Me</button>
<script>
function fetchData() {
    fetch('https://api.example.com/data')
        .then(response => response.json())
        .then(data => console.log(data));
}
</script>

<button onclick="fetchData()">Click Me</button>
<script>
function fetchData() {
    fetch('https://api.example.com/data')
        .then(response => response.json())
        .then(data => {
            console.log(data);
            // 在这里处理数据
        })
        .catch(error => console.error('Error:', error));
}
</script>

<button onclick="handleClick(event)">Click Me</button>
<script>
function handleClick(event) {
    event.preventDefault(); // 阻止默认行为
    event.stopPropagation(); // 停止事件冒泡
    alert('Button clicked!');
}
</script>