实现一些小功能（月影老师）

function isPrime(number){
    var result = true; 
    var temp = Math.sqrt(number);
    if(number <= 1){ return false;}
    for(var i = 2; i <= temp;i++){
        if(number%i===0){
            result=false;
            break;
        }
    }
    return result;
}
//test
console.log(isPrime(7));

function isArray(arr) {
    return Array.isArray(arr)||Object.prototype.toString.call(arr)==='[object Array]';
}
//test
console.log(isArray([1,2,3,4,5]));

function isString(str) {
    return Object.prototype.toString.call(str)==='[object String]';
}
//test
console.log(isString("abcdefg"));

// method first
function reverseStr(str){
    var arr=[].slice.call(str);
    arr.reverse();
    return result = arr.join("");   
}
console.log(reverseStr("abcdefg"));
//  method second
function reverse(str){
    var temp = [];
    for(var i=str.length-1; i>=0; i--){
        temp.push(str.charAt(i));
    }
    return temp.join("");
}
//test
var str = "abcdefghi";
console.log(reverseStr(str));
console.log(reverse(str));

//单个化
function normalize(arr) {
    if (arr && Array.isArray(arr)) {
        var i, len, map = {};
        for (i = arr.length; i >= 0; --i) {
            if (arr[i] in map) {
                arr.splice(i, 1);
            } else {
                map[arr[i]] = true;
            }
        }
    }
    return arr;
}
//生成0~100之间的随机整数组成长度为100的数组
function randomArr() {
    var res=[];
    var i;
    for( i = 0; i < 100; i ++ ){
        res.push(Math.floor(Math.random()*100));
    }
    return res;
}
//test
var input = randomArr();

// 加上一个排序，为了方便观察是否实现去重
input.sort(function (a, b) {
    return a - b;
});
console.log(input);

normalize(input);
console.log(input);

//slice函数返回一个数组（部分）的浅拷贝，为一个新数组对象
function argumentsToArray(param){
    return Array.prototype.slice.call(param);
}
function test(){
    var args = argumentsToArray(arguments);
    return Object.prototype.toString.call(args) === '[object Array]';

}
console.log(test(1, 2, 3, 4));

//考察点argument转数组
function sum(){
    var arr = Array.prototype.slice.call(arguments);
    var sum = 0;
    for(var i = 0, len = arr.length; i < len; i++){
        sum += arr[i];
    }
    return sum;
}
//test
console.log(sum(1, 2, 3, 4));
console.log(sum(1, 2));

//考察点：不能用sort函数实现数字型数组排序，但可以实现字符串型数组按首字母排序
var arr=[13,24,3,5,56,78,9];
arr.sort(function(n1,n2){
  return n1-n2;
});
console.log(arr[1]);

//与上面思路相同
var arr = [1,2,3,4,5,6,7,8,0];
arr = arr.sort(function(n1,n2){
    return Math.abs(n1-3)-Math.abs(n2-3);
});
console.log(arr);

function flat(data, result) {
    var i, d, len;
    for (i = 0, len = data.length; i < len; ++i) {
        d = data[i];
        if (typeof d === 'number') {
            result.push(d);
        } else {
            flat(d, result);
        }
    }
}
//test
var data =  [1, [2, [ [3, 4], 5], 6]];
var result = [];
flat(data, result);
console.log(result);

//方法一
Array.prototype.getRandomArray = function(){
    this.sort(function(a, b){
        return Math.random() - 0.5;
    });
    return this;
}
var arr = [];
for(var i = 0; i < 100; i++){
    arr[i] = i;
}
console.log(arr.getRandomArray());

//方法二
//先定义一个生成随机数的函数rand
function rand(a,b){
    return Math.floor(Math.random()*(b-a)+a);
}
//再定义数组打乱的函数
function getRandomArray(arr){
    var result = [];
    var len = arr.length;
    for(var i = 0; i < len; i++ ){
        var num = arr.splice(rand(0,arr.length),1)[0];
        result.push(num);
    }
    return result;
}
arr = [1,2,3,4,5,6,7,8];
console.log(getRandomArray(arr));

// method first
Array.prototype.getSumOfMaxOddAndMinEven = function(){
    var oddArr = [],
        evenArr = [];
    for(var i = 0, len = this.length; i < len; i++){
        if(this[i] % 1 !== 0){
            console.log("不是整数数组");
            return;
        }
        if(this[i] % 2 == 0){
            evenArr.push(this[i]);
        }else{
            oddArr.push(this[i]);
        }
    }

    oddArr.sort(function(a, b){
        return b - a;
    });
    evenArr.sort(function(a, b){
        return a - b;
    });

    if(oddArr.length > 0 && evenArr.length > 0){
        return oddArr[0] + evenArr[0];
    }else{
        return null;
    }
}
//method second use filter
Array.prototype.getSumOfMaxOddAndMinEven = function(){
    for(var i = 0, len = this.length; i < len; i++){
        if(this[i] % 1 !== 0){
            console.log("不是整数数组");
            return;
        }
    }
    var oddArr = this.filter(function(a){
        return a % 2 == 1;
    });

    var evenArr = this.filter(function(a){
        return a % 2 == 0;
    });

    if(oddArr.length == 0 || evenArr.length == 0){
        return null;
    }else{
        return Math.max.apply(null, oddArr) + Math.min.apply(null, evenArr);
    }
}
//测试用例

var arr = [1, 2, 3, 4, 5];
console.log(arr.getSumOfMaxOddAndMinEven());//7

var arr = [2, 4, 6];
console.log(arr.getSumOfMaxOddAndMinEven());//null

var arr = [1, 3, 5];
console.log(arr.getSumOfMaxOddAndMinEven());//null

var arr = [-1, 0, 1];
console.log(arr.getSumOfMaxOddAndMinEven());//1

var arr = [1.1, 2.1, 3, 4, 5];
console.log(arr.getSumOfMaxOddAndMinEven());//不是整数数组

//思路: 将字符串反转之后，与原字符串比较；
function ishuiwen(str){
    var str1 = [].slice.call(str).reverse().join('');
    if(str1 === str){
        return true;
    }
    else{
        return false;
    } 
}
console.log(ishuiwen("abcdedcba"));
console.log(ishuiwen("abcdecba"));

//方法一 思路: 从低位转化，再反转；
function mulBase(num, base){
    var arr = [];
    for(;num > 0;){
        arr.push( num % base );
        num = Math.floor(num / base);
    }   
    console.log(arr);
    return arr.reverse().join('');      
}
//方法二 思路: 从低位转化，数组前面插入
function mulBase2(num, base){
    var arr = [];
    for(;num > 0;){
        arr.unshift( num % base );
        num = Math.floor(num / base);
    }   
    console.log(arr);
    return arr.join('');    
}

console.log(mulBase(64,8));
console.log(mulBase2(64,8));