JS数组

JS 数组

 <script>
        'use strict';
        var arr = [1, 2, 3, 4, 5, "1"];
        var array = [1, 2, 3, 4, 5, "1"];
        console.log(arr);

        /*数组长度,可变化,赋值过大，增加空值；赋值过小，会丢失元素*/
        console.log(arr.length);
        arr[2] = 0;
        console.log(arr);
        arr.length = 10;
        console.log(arr);
        arr.length = 3;
        console.log(arr);

        /*indexOf通过元素获取下标，字符串的"1"和数组1是不同的*/
        console.log(array.indexOf(1));
        console.log(array.indexOf("1"));

        /*截取第几到第几的元素*/
        console.log(array.slice(1));
        console.log(array.slice(1, 3));

        /*push尾部压入元素，pop尾部弹出元素*/
        array.push("a", "b");
        console.log(array);
        array.pop();
        console.log(array);

        /*unshift压入头部,shift弹出头部第一个元素*/
        array.unshift("a", "b");
        console.log(array);
        array.shift();
        console.log(array);

        /*sort排序*/
        console.log(array.sort());

        /*reverse元素反转*/
        console.log(array.reverse())

        /*concat,返回一个新数组，原数组并没有改变*/
        console.log(array.concat(9, 9, 9));
        console.log(array);

        /*join连接符,使用特定的符号连接*/
        console.log(array.join('->'))

        /*多维数组*/
        let num = [[1,2],[3,4],[5,6]];
        console.log(num[1][1]);


    </script>