30js基础，数组

<head>
    <meta charset="UTF-8">
    <title>js数组</title>
</head>
<body>
        <script>
            //声明
            var arr1 = [];
            var arr2 = new Array();
            document.writeln("arr1长度为:"+arr1.length+"<br>");
            document.writeln("arr2长度为:"+arr2.length+"<br>");

            var arr3 = [10];
            var arr4 = new Array(10);
            document.writeln("arr1长度为:"+arr3.length+"<br>");
            document.writeln("arr2长度为:"+arr4.length+"<br>");

            var arr5 = [10,"apple"];
            var arr6 = new Array(10,"apple");
            document.writeln("arr1长度为:"+arr5.length+"<br>");
            document.writeln("arr2长度为:"+arr6.length+"<br>");
            document.writeln("<hr>");

            //2:通过下标使用元素
            arr1[9] ="asd";
            document.writeln("arr1长度为:"+arr1.length+"<br>");
            document.writeln("<hr>");
            //3:将元素添加到数组末尾
            arr2.push(123);
            document.writeln("arr2长度为:"+arr2.length+"<br>");
            document.writeln("<hr>");
            //4:数组的遍历
            var arr7 = [1,3,4,5,6,7,8,];
            for(var i=0;i<arr7.length;i++){
                document.writeln(i+1+":"+arr7[i]+"<br>");
            }
            document.writeln("<hr>");

            //增强for未定义的就会被跳过
            for(var i in arr7){
                document.writeln((i+1)+":"+arr7[i]+"<br>");
            }
            document.writeln("<hr>");
            //使用join方法,未定义的按空字符串走
            document.writeln(arr7.join("<br>"));
            document.writeln("<hr>");

            document.writeln(arr7.join(","));
            document.writeln("<hr>");
            //多维数组

            var arr9 = [
                [1,2,3],[4,5,6]
            ];

            var arr10 = [
                [[1,3,4],[5,6,7],[1,3]],[[6,7],[8,9],[3,4]]
            ];
            document.writeln("<hr>");

            //构建三角形
            var arr11 = [];
            var line = "*";

            for (var i = 0; i <10 ; i++) {
                arr11.push(line);
                line+=" *";
            }
            document.writeln(arr11.join("<br>"));
            document.writeln("<div style='text-align: center'>"+arr11.join("<br>")+"</div>");
        </script>

</body>
posted on 2022-04-10 23:37 小小程序猿level1 阅读(25) 评论(0) 收藏举报