js 去掉字符串最后一个逗号 “，”

待处理字符串：

var str = "1,2,3,4,5,";
方法1：slice()

alert(str.slice(0,-1))
alert("1,2,3,4,5,".slice(0,-1))

方法1：substring()
("1,2,3,4,5,".substring("1,2,3,4,5,".length-1)==',')?"1,2,3,4,5,".substring(0,"1,2,3,4,5,".length-1):"1,2,3,4,5,";
str=(str.substring(str.length-1)==',')?str.substring(0,str.length-1):str;