<script type="text/javascript">

var a = [];

a[50] = 50;

alert(a.length);

</script>

请问数组a有多少个元素, 或者换一句话说, 数组a的长度为多少?

<script type="text/javascript">

var a = [];

a['age'] = '18';

a['sex'] = 'Male';
a['site'] = 'http://www.qSyz.net';

alert(a.length);

</script>

<script type="text/javascript">
var a = {'age':30,'sex':'male'};

alert(a.length);

</script>

<script type="text/javascript">

function count(o){
var t = typeof o;

if(t == 'string'){
return o.length;

}else if(t == 'object'){

var n = 0;

for(var i in o){

n++;

}

return n;
}
return false;

}

</script>

现在在测试一下刚才的例子?

<script type="text/javascript">

var a = [];

a[50] = 50;

alert(count(a));

</script>

得到结果为2

<script type="text/javascript">

var a = [];

a['age'] = '18';

a['sex'] = 'Male';
a['site'] = 'http://www.qSyz.net';

alert(count(a));

</script>

得到结果为3.

<script type="text/javascript">
var a = {'age':30,'sex':'male'};

alert(count(a));

</script>

得到结果为2