1.假设法

 var arr = [1231,252,234];
    var max = arr[0],min = arr[0];

    for(var i=0;i<arr.length;i++) {
       max < arr[i] ?max= arr[i]: null;
        min > arr[i] ?min= arr[i]: null;
    }
    console.log(min,max);

2.sort法

var arr= [443,44334,12];
    arr.sort(function (a,b) {
        return a - b;
    })
    var min = arr[0],max = arr[arr.length - 1];
    console.log(min,max);

3.Math.min + eval()

 var arr = [4343,44,42242424];
    var minstr = "Math.min("+arr.toString()+")";
    var min = eval(minstr);
    console.log(min);

4.apply + Math.min

   var arr = [4343,44,42242424];
    var min = Math.min.apply(null,arr);
    console.log(min);