function getMaximin (arr,maximin) {
if (maximin == "max") {
return Math.max.apply(Math, arr);
}else if (maximin == "min") {
return Math.min.apply(Math, arr);
}
}

var a = [3,2,4,2,10]

var b = [12,4,45,786,9,78]

alert("aMax:" + getMaximin(a,"max") + "---aMin:" + getMaximin(a,"min") + "---bMax:" + getMaximin(b,"max") + "---bMin:" + getMaximin(b,"min"))//aMax:10---aMin:2---bMax:786---bMin:4