Simple explanation about the array

The next day 1

Array element

    // 创建一个数组元素
    var arr = ['a','b','c','d'];
    // alert(arr); 显示数组内容
    console.log(arr);//  显示数组
    // console.log(arr.length); 显示数组长度，因为数组排列从0开始，所以显示的长度会加一
    delete arr[2];
    console.log(arr);
    //通过delete删除数组元素会形成空位，空位因为没有数据所以是undefined
    //会形成稀疏数组
    //通过length删除数组元素
    //通过吧length属性设置为0，可以清空数组/如果数组本身length值就是0，那这种方式清空数组将会没有效果
    arr.length = 0;
    console.log(arr);

Change the query internal array

    var arr = ['a','b','c','d'];
    //更改
    arr[1]= 'x'
    arr[2]= 'y'
    console.log(arr);
    //现在查询数组元素
    console.log(arr[0]);
    console.log(arr.length);
    console.log(arr[arr.length-1]);//获取最后一个元素
    for(var i=0;i<arr.length;i++){
        console.log(arr[i])//从第0位开始逐步打印
    }

Multidimensional Arrays

//数组里可以储存任意类型数据
    //数组里面继续储存数组，我们通常把这样的数组称之为多维数组
    var arr1 = [
        ['张三', '李四'],
        ['王五', '赵六'],
        [
            ['皮皮虾', '我们走'],
            ['去找一个男朋友', [
                ['吃炸鸡', '喝啤酒']
            ]]
        ]
        ];
    console.log(arr1);
    // 输出李四
    console.log(arr1[0][1])
    console.log(arr1[2][1])
    console.log(arr1[2][1][1][0][1])

Delete Notes array

// 创建一个数组 
var arr = ['a','b','c','d','e'];

console.log(arr);

delete arr[2];

console.log(arr[2]);// 如果通过delete 删除，会形成空位，方位会为undefined

console.log(arr[10]);// 如果使用的索引值超出了范围，那么同样会显示undefined

But also by the array push increasing a length and returns a new array

    var arr = ['a','b','c']; // 创建一个数组  
    // push方法会通过返回值返回u一个新数组的长度
    arr.push('s','2')
    var info = arr.push
    console.log(arr);
    console.log(info);

Array by pop delete the last array method

    //通过pop方法进行删除 
    var arr = ['a', 'b', 'c', 'd', 'e', 'f', 'g'];

    var len = arr.length;


    for (var i = 0; i < len; i++) {
        console.log(arr.length)
        arr.pop();
    }
    console.log(arr);

Array by shift to achieve first proposed the array, then the array losing the first set, reordered from 0

    var arr = [1,2,3,4];

    var info = arr.shift();
    console.log(info);//此时提出的1
    console.log(arr);//此时数组：0：2，1：3........

By array unshift method to start adding in the first row of the array array

// unshift方法 
    var arr = [1,2,3,4];

    var a = arr.unshift('张晓桑','李晓丝');
    console.log(a); //此时显示长度6
    console.log(arr);//从零开始排序

Through the array: an array of all the calls and the like

    // 遍历数组  
    for(var i in arr){
    console.log(arr[i])
    }

The array in ascending order and back down appreciated :()

    var arr = [3,2,4,6,5,1,9,7,8,10];
    function sort(arr){

    for(var i=0;i<arr.length - 1;i++){
        // console.log(i)
        for(var j=0;j<arr.length - i -1;j++){
            if(arr[j] > arr[j+1]){
                var swap = arr[j];
                arr[j] = arr[j+1];
                arr[j+1] = swap;
                }
            }
        }
    } 
    sort(arr)
    console.log(arr)  

The second arrangement method

    function selectSort(arr){
        var len = arr.length;
        var minIndex,temp;

        for(var i=0;i<len-1;i++){
            minIndex = i; 
            for(var j=i+1;j<len;j++){
                if(arr[j] < arr[minIndex]){ // 找最小值
                    minIndex = j;
                }
            }
            temp = arr[i];
            arr[i] = arr[minIndex];
            arr[minIndex] = temp;
        }
    }
    selectSort(arr);
    console.log(arr)

Objects

// 创建一个对象  
    var obj = {};
    console.log(obj)
    /*
    属性:
        姓名 
        年纪
        爱好
        地址
        电话
    方法:
        跑步 
        唱歌
        旅游
    */
    // console.log(name)
    var xiaoming = {
        "name":"小明",
        age:35,
        like:"吃喝嫖赌",
        address:"浑南区",
        phone:"13209087979",
        run:function(){
            alert("啊，跑步累死啦!");
        },
        lvyou:function(){
            alert("xiaoming and xiaohong go lvyou,xiaohong say:today,me he an zhu zai where li");
        }
    };
    // xiaoming.noKnow = "哈哈哈，我也不知道是啥";
    // xiaoming.sayHello = function(){alert("hello,world")}
    // delete xiaoming.noKnow;
    // delete xiaoming.sayHello;
    // xiaoming.age = 18;
    console.log(xiaoming.name)
    console.log(xiaoming['name'])
    // console.log(xiaoming)
    // console.log(xiaoming.name);
    // xiaoming.run();
    // window.alert();

Random highlighted: achieved by binding between the array and the array length

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style type="text/css">
        #box {
            width: 300px;
            height: 300px;
            border: 20px solid rgb(181, 44, 44);
            line-height: 300px;
            text-align: center;
            font-size: 35px;
        }
    </style>
</head>

<body>
    <div id="box">
        点名
    </div>
    <button id="start">开始</button>
    <button id="stop">暂停</button>
</body>
<script>
    // 第一步：先创立一个数组来储存人名
    var name_list = ["王德法", "卢本伟", "李健", "郭美美","王子瑄"];
    var timer; //创建一个变量来储存定时器
    var oBox = document.getElementById('box');
    var start = document.getElementById('start');
    var stop = document.getElementById('stop');
    // 建立函数
    function changeName() {
        var num = Math.floor(Math.random() * name_list.length); //建立随机数，通过随机长度来绑定数组
        oBox.innerText = name_list[num];
        // console.log(oBox.innerText);
        // console.log(num);
        timer = setTimeout("changeName()", 50);
    }
    // changeName() 
    start.addEventListener('click',function(){
    changeName()
    // console.log(name);
})


stop.addEventListener('click',function(){
    //清空时间
    clearTimeout(timer)
    // console.log(name);
})
</script>

</html>