Javascript Arrays在数组项之前打印undefined

Question

我在javascript中打印一个简单的数组列表时遇到问题.仅在两个数组项之前打印undefined.请考虑以下代码;

function buildList(){
    var box = document.getElementById("box");
	var startList  = "<ol>";
	var endList = "</ol>";
	var listItems;
      
        var arry = ["Go to shopping", "Go to Mall"];
  	for(var i = 0; i < arry.length; i++){
            listItems += "<li>" + arry[i] + "</li>";
	}

	box.innerHTML = startList + listItems + endList;
}
document.onLoad(buildList());``
          

<div id="box">
  
</div>

输出是

undefined 1)去购物2)去购物中心

请帮忙.

Answer 1

您的listItem变量未定义,因为它未初始化.

var listItems = "" ; (在第5行)应该解决你的问题.