正则表达式

(\w)[^\1]{0,}\1

jquery实现

//校验重复
function checkRepeated(str) {
      var reg = /(\w)[^\1]{0,}\1/g;
      return reg.test(str);
}

var flag = checkRepeated(course);
if (flag) {
	$.modal.alertError("字符串："+course+"<br/>是否有重复："+flag);
	return false;
}

校验效果

或循环遍历校验

//校验重复信息
//var str = "40,42,45,46,42,43,41,40";
function checkRepeated(str) {
	str = str.substring(0,str.lastIndexOf(","));
	var strs = str.split(",");
	var length = strs.length;
	for (var i = 0; i < length-1; i++) {
		for (var j = i+1; j < length; j++) {
			if (strs[i] == strs[j]) {
				return true;
			}
		}
	}
	return false;
}