var arr = [9,8,55,66,49,68,109,55,33,6,2,1];
  
var max = arr[0];

function findMax( i ){
  if( i == arr.length ) return max;
  if( max < arr[i] ) max = arr[i];
  findMax(i+1);
}
 
findMax(1);
console.log(max);

var arr = [9,8,55,66,49,68,109,55,33,6,2,1];  
var max = arr[0];
for(var i = 1; i < arr.length; i++){
  if( max < arr[i] ){
    max = arr[i];
  }
}

console.log(max);

Math.max.apply(null,[9,8,55,66,49,68,109,55,33,6,2,1])

var a=[1,2,3,5];
alert(Math.max.apply(null, a));//最大值
alert(Math.min.apply(null, a));//最小值

var a=[1,2,3,[5,6],[1,4,8]];
var ta=a.join(",").split(",");//转化为一维数组
alert(Math.max.apply(null,ta));//最大值
alert(Math.min.apply(null,ta));//最小值