3.数组的其它方法

3.1 join 将数组拼接成字符串

        var arr =[ "html","css","js"];
        /* join(seprate)  -->可以将数组拼接成字符串 */;
        console.log(arr.join(""))
        console.log(arr.join("|"));
        console.log(arr.join(" "));
        console.log(arr.join("*"));
        console.log(typeof arr.join(""))

例子

    <div id="app"></div>
    <script>
        var dates = ["2019","03","09"]
        /* 2019-03-09 */
        var str = dates.join("-");
        console.log(str)
        var app = document.getElementById("app");
        app.innerHTML =str; //2019-03-09
    </script>

3.2 sort 排序

升序

        var arr = [12,3,5,11,1];
        console.log(arr.sort())
        /* 得到从小到大的数据结构 */
        /* 
        arr.sort(function(a,b){
            return a-b;
        })
         */
        var newArr = arr.sort(function(a,b){
            return a-b;
        })
        console.log(newArr)

降序

        var  c = [12,14,45,2]
        /* 
        降序
        arr.sort(function(a,b){
            return b-a;
        })
         */
        var test = c.sort(function(a,b){
            return b-a;
        })
        console.log(test)

3.3 reverse 反转

        var arr = ["html","css","js"];
        arr.reverse();
        console.log(arr);