扩展

1-1排序

• sort

  /* sort排序 升序 a-b  降序b-a */
        var arr = [21,12,33,31,7]
        var c = arr.sort((a,b)=>{
            return b-a;
        })
        console.log(c)

  for循环去排序

for(let i=0;i<arr.length;i++){
            for(let i=0;i<arr.length;i++){
            if(arr[i]>arr[i+1]){
                var temp = arr[i]
                arr[i]= arr[i]
                arr[i]=arr[i+1]
                arr[i+1] = temp;
            }
        }
        }

1-2求和

• sum

  <script>
        var arr = [1,2,3,4]
        /* var sum = arr.reduce((a,b)=>{
            return a+b;
        }) */
        var sum = 0;
        for(var i=0;i<arr.length;i++){
            sum+=arr[i];
        }
        console.log(sum)
    </script>
  

  1-3反转

• reverse

  <script>
        /* 反转 */
        var arr = [11,13,14]
        arr.reverse();
        console.log(arr)
    </script>
  

  1-4最大值、最小值

<script>
        var arr = [1,2,3,4];
        Array.from(arr,item=>{
            console.log(item)
        })
        var max = Math.max(...arr);  /* 取最大值 */
        var min = Math.min(...arr);  /* 取最小值 */
        console.log(max)
        console.log(min)
    </script>

1-5arr

执行结果：

<script>
        var arr = [1,2,3,4,5]
        var newArr = arr.filter(item=>{
            return item>3;
        })
        console.log(newArr)
    </script>

1-6copywithin

执行结果：

<script>
        var arr = ['html','css','javascript','vue'];
        var newArr = arr.copyWithin(2,1);
        console.log(newArr)
        var arr =[1,2,3,4]
        var num = arr.some(item=>{
            return item>3;
        })
        var str = arr.every(item=>{
            return item>1;
        })
        var value = arr.find(item=>{
            return item>2;
        })
        console.log(num)
        console.log(str)
        console.log(value)
    </script>

1-7 equal

<div>hello world</div>
        <div>hello world</div>
        <div>hello world</div>
        <div>hello world</div>
        <script>
            /* equal */
            var $div = $("div").eq(0)
            console.log($div)
        </script>

1-8join

讲数组拼接成字符串

var a= ["喜剧","动画","冒险"]；
b= a.join"|";    //输出：喜剧|动画|冒险