js数组定义与数组长度

var a = new array();

var b = new array(8);

var c = new array("first", "second","third");

或者数组直接量：

var d = ["first", "second","third"];

下面看一下，在数组后面增加一个元素

var myarray = [];

myarray[myarray.length] = 'new element';

数组的长度

array只有一个属性，就是length，length表示的是数组所占内存空间的数目，而不仅仅是数组中元素的个数，在刚才定义的数组中，b.length的值为8

<script>

var a = new array("first", "second","third")

a[48] = "12"

document.write(a.length)

//显示的结果是49

</script>

下面来看看修改数组长度实例

var myarray = [1,2,3];

myarray.length // 3

myarray.length = 2; //delete the last element

myarray.length = 20 // add 18 elements to the array; theelements have the undefined value.