How do I resolve this “Undefined function” JavaScript Error?

Question

I keep getting a "Undefined function" JavaScript error in my error console. Any idea why?

<div id="counter" style="width: 40px;"></div>

<script type="text/javascript">
    var seconds = 60
    document.getElementById('counter').innerHTML = seconds

    function countDown() {
        if(seconds <= -1) {
            seconds += 1
        } else {
            seconds -= 1
            document.getElementById('counter').innerHTML = seconds
            setTimeout("countDown()", 1000)
        }
    }

    countDown();
</script>

Answer 1

您可能要考虑添加一些分号。

Answer 2

The undefined function may be document.getElementById if you execute this piece of code before the document is loaded. But I could be wrong.

Answer 3

对我而言，它的值为-1，即您在“ if”语句中的值。