数组

1.数组的创建
var arr1 = new Array();//创建一个空数组
var arr2 = new Array(3);//创建一个长度为3的数组；
var arr3 = new Array("小张","小黄","小明");
//创建一个数组，数组内容为："小张","小黄","小明"
var arr4 = ["小张","小黄","小明"];
//
console.log(arr1,arr2,arr3,arr4);

2.星期几
var arr = ["星期日","星期一","星期二","星期三","星期四","星期五","星期六"];
var d = new Date();
var D =d.getDay();//0-6
console.log("今天是",arr[D]);

3.数组遍历
var arr = ["小黄","小明","小张","小王"];
//一个一个输出数组的值；
//数组下标从0开始
//数组的长度 length
//循环要点 1：循环的初始值第0个；
// 2:循环的结束条件length-1;
// 3:循环操作,输出元素
for(var i=0;i<=arr.length-1;i++){
console.log(arr[i])
}
console.log(i);

4.数组排序
var arr = [1,5,15,199,20,35,40,60,300,5.6];
arr = arr.sort();
console.log("一般排序结果",arr);

    //升序
    function asc(a,b){
        if(a>b){
            return 1;
        }else{
            return -1;
        }
    }
    
    //降序
    function desc(a,b){
        if(a>b){
            return -1;
        }else{
            return 1;
        }
    }
    
    var arr1 = arr.sort(asc);
    console.log("排序结果asc",arr1);
    
    var arr2 = arr.sort(desc);
    console.log("排序结果desc",arr2);

5.数组与字符串转换
var str ="我-好-中意你-呀-靓-仔-!";
//把字符串转换为数组
var arr = str .split("-");
//把str分割为数组，分割符为-;
console.log(arr);

    var str2 ="我好中意你呀靓仔!";
    var arr2 = str2.split("");
    console.log("字符分割后的数组",arr2);
    
    arr2. reverse();//反转数组
    console.log("翻转后的数组",arr2);
    
    var str3 = arr2.join("");//把数组转换为字符串，连接符为空
    console.log(str3,str2);