javascript生成的文本框如何获取值，谢谢！

{
var str = "";
var allContainedElements = document.getElementsByTagName('input');
alert(allContainedElements.length);
for (var b = 0; b < allContainedElements.length; b++)
{

alert(allContainedElements[b]);

}

}

</script>

<script type='text/javascript'>

alimama_pid='mm_13314150_0_0';
alimama_type='g';
alimama_tks={};
alimama_tks.style_i=1;
alimama_tks.lg_i=1;
alimama_tks.w_i=500;
alimama_tks.h_i=69;
alimama_tks.btn_i=1;
alimama_tks.txt_s='';
alimama_tks.hot_i=1;
alimama_tks.hc_c='#999999';
alimama_tks.c_i=0;
alimama_tks.cid_i=0;
\ </script>


<input name="btnShow" type="button" value="显示" onclick="javascript:btnShow_rtn();" />


<script type='text/javascript'  src='http://a.alimama.cn/inf.js'> </script>


<!--上面的代码生成两个文本框，请问js生成的文本框值如何获取。谢谢-->

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<script language="javascript">
function btnShow_rtn()
{
var str = "";
var allContainedElements = document.getElementsByTagName('inpu