為什么此動畫功能不起作用？

Question

所以這段代碼有效：

<script>
function animate() {
    var x = 0;
    var goUp = document.getElementById('rotationUp');
    var comeDown = document.getElementById('rotationDown');

    goUp.onmouseover = alert(x);
}
</script>

這不是：

<script>
function animate() {
    var x = 0;
    var goUp = document.getElementById('rotationUp');
    var comeDown = document.getElementById('rotationDown');

    goUp.onmouseover = function() {
    alert(x);
    }
}
</script>

唯一的區別是function ，我在哪里出錯？

PS：我需要它作為功能

Answer 1

嘗試

function animate() {
    var x = 0;
    var goUp = document.getElementById('rotationUp');
    var comeDown = document.getElementById('rotationDown');

    goUp.onmouseover = function() {
        alert(x);
    }
}

Answer 2

嘗試將x變量全局放置：

<script>
var x = 0;

function animate() {
    var goUp = document.getElementById('rotationUp');
    var comeDown = document.getElementById('rotationDown');

    goUp.onmouseover = function() {
        alert(x);
    }
}
</script>

如果不起作用，請嘗試window.x ：

        alert(window.x);

或this.x ：

        alert(this.x);