无法读取未定义的属性'split' - 将数组元素（字符串）拆分为数组元素（更多字符串）

Question

我最近开始使用JavaScript进行编码，并且正在为课程项目执行此操作。所以，我想要做的是从textarea中获取拼接数据（以这种形式：artist | album | year | genre | rating），然后对其进行处理，以便在表单后将它们放入表中。

    <form name="viewform" enctype="text/plain">
        <table class="center" id="table0" name="table0">
    <!-- Here is the textarea and an onClick activated button -->
        </table>
        <table class="center" id="table1" name="table1">
            <tr>
                <th>Artist</th><th>Album</th><th>Year</th><th>Genre</th><th>Rating</th>
            </tr>
        </table>
        <script type="text/javascript">
        // viewScript() is for processing input from a textarea and setting it into HTML tables
        function viewScript() {
            var textArea = String(document.getElementById('textarea'));
            var arrayTextarea = textArea.split('\n'); // Every line becomes a string element in the array
            var arrayTextareaLength = arrayTextarea.length; // Count number of elements in arrayTextarea
            var table = document.getElementById('table1');
            var i, x;
            for (i=0; i <= arrayTextareaLength; i++) {
                var miniArray = arrayTextarea[i].split('|'); // Each string element in arrayTextarea becomes split into elements in miniArray. Each loop, miniArray changes to the next line
    /* Below is a loop to insert miniArray[i] into table1 */
                }
            }
        }
        </script>
    </form>

问题出在for循环打开后的行中。开发人员的控制台告诉我，它无法读取未定义的属性“拆分”。我做错了什么？