JavaScript 字符串比较：判断两个字符串是否相同怎么判断

var responseValue = xhr.responseText.toString();//ajax获取的后台传的值，值为“NO”

var NO = "NO".toString();

alert("responseValue--" + responseValue);

alert("NO--" + NO);

alert("111");

alert("responseValue == NO--:"+(responseValue == NO));

alert("xhr.responseText==NO-----" + (xhr.responseText == "NO"));