javascript - 为什么这个动画功能不起作用？

Question

所以这段代码可以工作:

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

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

这不是:

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

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

唯一的区别是功能，我哪里出错了？

PS:我需要它作为一个函数来工作

Answer 1

尝试

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

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