js数组操作 求最大值，最小值，正序、倒叙大小值排序，去重复

var arr = [1,5,2,56,12,34,21,3,5]

Math.min.apply({},arr)  // 1
Math.max.apply({},arr)  // 56

arr.sort((m,n)=>m-n)    // [1, 2, 3, 5, 5, 12, 21, 34, 56]
arr.sort((m,n)=>n-m)   //[56, 34, 21, 12, 5, 5, 3, 2, 1]

去重复

var arr = [2,1,4,3,2,4,2,3,4,2,6,5,5]
var obj = {};
var arrNew = [];
for(var i=arr.length-1;i>=0;i--){
    if(!obj[arr[i]]){
        obj[arr[i]] = true;
        arrNew.push(arr[i]);
    }
}
console.log(arrNew,obj)
// [5, 6, 2, 4, 3, 1]

Array.prototype.unique2 = function(){
    this.sort(); //先排序
    var res = [this[0]];
    for(var i = 1; i < this.length; i++){
        if(this[i] !== res[res.length - 1]){
            res.push(this[i]);
        }
    }
    return res;
}
var arr = [1, ‘a‘, ‘a‘, ‘b‘, ‘d‘, ‘e‘, ‘e‘, 1, 0]
console.log(arr.unique2());