js生成指定位數的校驗碼

//js生成指定位數的校驗碼
var chars = ['0','1','2','3','4','5','6','7','8','9',
'a','b','c','d','e','f','g','h','i','j','k','l','m',
'n','o','p','q','r','s','t','u','v','w','x','y','z',
'A','B','C','D','E','F','G','H','I','J','K','L','M',
'N','O','P','Q','R','S','T','U','V','W','X','Y','Z'];
function generateMixed(n) {
	var res = "";
	for(var i = 0; i < n ; i ++) {
		var id = Math.ceil(Math.random()*61);
		res += chars[id];
	}
	return res;
}
console.log(generateMixed(6)); //79i2aP