Js-创建数组、访问数组

数组

创建数组：

最常用：var arr = [ ];

<script>/*var arr = new Array();arr [0] = "zhangsan";arr [1] = "lisi";arr [2] = "wangwu";for(var i= 0;i<arr.length;i++){alert(arr[i]);}*/var arr=newArray(2);arr[0] ="zhangsan";arr[1] ="lisi";arr[2] ="wangwu";for(vari=0;i<arr.length;i++) {alert(arr[i]);}var arr=newArray("zhangsan","lisi","wangwu");arr[0] ="zhangsan";arr[1] ="lisi";arr[2] ="wangwu";for(vari=0;i<arr.length;i++) {alert(arr[i]);}/*最简单*/var arr= ["zhangsan","lisi","wangwu"];arr[0] ="zhangsan";arr[1] ="lisi";arr[2] ="wangwu";for(vari=0;i<arr.length;i++) {alert(arr[i]);}</script>

访问数组：

通过索引值访问数组

<script>var arr= ["zhangsan",1,2,3];alert(arr[3]);alert(arr.length);</script>

数组方法：

<script>var arr= ["zhangsan","lisi","wangwu",6];/*join方法：将数组元素按照指定的分隔符进行分隔，返回一个字符串*/var newArr=arr.join();document.write(newArr);/*concat：可以同时连接元素和数组*也可以单独连接元素，或者单独连接数组*/var arr2= ["wangba","baijiu"];var newArr=arr.concat("tianqi");var newArr=arr.concat(arr2);var newArr=arr.concat("tianqi",arr2);document.write(newArr);/*push：在数组末尾添加一个或多个数组元素，返回数组长度*/arr.push("tianqi","wangba","baijiu");document.write(arr);/*pop：删除并返回数组的最后一个元素*/var deleted=arr.pop();document.write(deleted);document.write("<br>");document.write(arr);/*shift：删除并返回数组的第一个元素*/var deleted=arr.shift();document.write(deleted);document.write(arr);/*unshift：在头部插入数组元素，返回数组长度*/var newArr=arr.unshift("xiaoer");document.write(newArr);document.write(arr);/*sort：排序*/var newArr=arr.sort();document.write(newArr);/*数字排序*/function sortNumber(a, b) {returna - b;}var arr= [9,10,15,62,53,42];var newArr=arr.sort(sortNumber);document.write(newArr);/*reverse：数组倒序*/var newArr=arr.reverse();document.write(newArr);/*splice：删除或添加数组元素*删除元素的索引值 （添加元素的索引值） 如果第一个参数为负值，从结尾开始删除。*删除数量*进行填补的数据*/var newArr=arr.splice(1,1,"wangba");document.write(arr);document.write("<br>");document.write(newArr);/*slice：截取元素 （操作数组元素都是前包后不包）*截取起点索引值（包含）*截取终点索引值（不包含） 不写，默认截取到最后一个*/var newArr=arr.slice(-1);var newArr=arr.slice(1);var newArr=arr.slice(1,3);document.write(arr);document.write(newArr);</script>

传值和传引用

<script>/*基本数据类型：传值*/var zhangHeight=180;var lisiHeight=zhangHeight;zhangHeight=185;alert(lisiHeight);/*基本数据类型：传引用*/var zhangSan= [180,80];var liSi=zhangSan;zhangSan[0] = 185;zhangSan[1] = 85;alert(liSi[0]);alert(liSi[1]);</script>

数字的定义和使用：

<script>var myNum=newNumber(4);var myNum=5;alert(Number.MAX_VALUE);/*最大的数*/alert(Number.MIN_VALUE);/*最小的数*/alert(Number.NEGATIVE_INFINITY);/*负无穷大*/alert(Number.POSITIVE_INFINITY);/*无穷大*/</script>

NaN：not a number

任意类型数据-->字符串：

/*把数字转换为字符串，可以转换数字，数组，Boolean类型的数据*/

数字

var i=5;var j=i.toString();alert(typeof(j));

数组

var arr= ["zhangsan","lisi"];var result=arr.toString();alert(typeof (result));

Boolean

var isTrue=true;var result=isTrue.toString();alert(typeof (result));

/*字符串长度*/

var s="jieruijiaoyu";alert(s.length);