javascript 输出异常，本应是数字，却输出 NaN

function RelativePoint(a,b,c) {
		this.a = a;
		this.b = b;
		this.c = c;
	} 
	function sortNumber(a,b)
	{
		return a - b
	}
	function fpos2(pos) {
		var n = new Array(-pos.a, pos.b, -pos.c);
		n.sort(sortNumber);
		alert(pos.a+n[1] + "," + pos.b-n[1] + "," + pos.c+n[1]);
	}
	<input type="button" name="test2" value="test2" onclick="fpos2(new RelativePoint(2,-3,-1))" />

补充：哦，谢谢， pos.a+n[1] 等三个値本想给一个数赋值来着，临时改成联接成字符串显示，没注意，头次碰上这问题

答案：alert(parseInt(pos.a+n[1]) + "," + parseInt(pos.b-n[1])+ "," + parseInt(pos.c+n[1]));
根据从左到右结合性 在：
alert(pos.a+n[1] + "," + pos.b-n[1] + "," + pos.c+n[1]);
pos.a+n[1] + "," + pos.b 已为字符串"0,-3"然后是字符串再数字n[1]就会显示为NaN！
所以也可以这样
 alert((pos.a+n[1]) + "," + (pos.b-n[1]) + "," + (pos.c+n[1]));

其他：alert((pos.a+n[1]) + "," + (pos.b-n[1]) + "," + (pos.c+n[1]));
应该这样写，因为“+”既是连接符又是运算符，当然会出错。 

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