TypeError: Cannot read properties of undefined (reading 'toUpperCase') at dispatchXhrRequest

这个错误是由于在字符串拼接的过程中出现了undefined的情况，导致无法读取属性toUpperCase而引发的TypeError错误。具体来说，代码中的循环条件`i <= ia.length`导致了取到了空值，即`ia[i`可能为undefined，从而无法执行`ia[i].slice(0, 1)`。这是因为数组的索引是从0开始计数的，而数组的长度是从1开始计数的，所以条件应该改为`i < ia.length`。此外，还应该在对`ia[i`进行判断，以避免出现undefined的情况。下面是修改后的代码：

var str2 = "get-element-by-class-name";
var ia = str2.split("-");
var nStr = '';
for (var i = 0; i < ia.length; i++) {
  var a = (ia[i || '').slice(0, 1);
  var b = (ia[i || '').slice(1);
  var c = a.toUpperCase() + b;
  nStr += c;
}
console.log(nStr);

这样修改后，就能正确拼接字符串并输出结果"getElementByClassName"了。<span class="em">1</span><span class="em">2</span><span class="em">3</span>
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