我正在尝试在我的网站上创建一个按钮，允许您在单击时下载数据。此链接应根据我所拥有的4个下拉菜单中的选定值进行更新。问题是我的代码不起作用。以下是代码：
<script>
function set_st(t) {
var sel_el = t.options[t.selectedIndex]
document.getElementById('my-iframe').src = 'http://watermonitor.gov/naww/index.php?st=' + sel_el.value
}
function set_st(t) {
var sel_el = t.options[t.selectedIndex]
document.getElementById('down').src = 'http://watermonitor.gov/naww/index.php?st=' + sel_el.value
}
</script>
<header>
<div id='map_container' style="margin-top: 100px; border: 0px solid red; text-align: center;">
<div id="xbuilder">
<table>
<tbody>
<tr>
<td>
<div>
United States:
<span data-tooltip='Choose a US state'>
<select name='usst' id='usst' size='1' onchange='set_st(this);' >
<option value=''>States</option>
</option>
<option value='al'>Alabama</option>
<option value='ak'>Alaska</option>
<option value='az'>Arizona</option>
<option value='ar'>Arkansas</option>
<option value='ca'>California</option>
<option value='co'>Colorado</option>
<option value='ct'>Connecticut</option>
<option value='de'>Delaware</option>
<option value='dc'>District of Columbia</option>
<option value='fl'>Florida</option>
<option value='ga'>Georgia</option>
<option value='hi'>Hawaii</option>
<option value='id'>Idaho</option>
<option value='il'>Illinois</option>
<option value='in'>Indiana</option>
<option value='ia'>Iowa</option>
<option value='ks'>Kansas</option>
<option value='ky'>Kentucky</option>
<option value='la'>Louisiana</option>
<option value='me'>Maine</option>
<option value='md'>Maryland</option>
<option value='ma'>Massachusetts</option>
<option value='mi'>Michigan</option>
<option value='mn'>Minnesota</option>
<option value='ms'>Mississippi</option>
<option value='mo'>Missouri</option>
<option value='mt'>Montana</option>
<option value='ne'>Nebraska</option>
<option value='nv'>Nevada</option>
<option value='nh'>New Hampshire</option>
<option value='nj'>New Jersey</option>
<option value='nm'>New Mexico</option>
<option value='ny'>New York</option>
<option value='nc'>North Carolina</option>
<option value='nd'>North Dakota</option>
<option value='oh'>Ohio</option>
<option value='ok'>Oklahoma</option>
<option value='or'>Oregon</option>
<option value='pa'>Pennsylvania</option>
<option value='ri'>Rhode Island</option>
<option value='sc'>South Carolina</option>
<option value='sd'>South Dakota</option>
<option value='tn'>Tennessee</option>
<option value='tx'>Texas</option>
<option value='ut'>Utah</option>
<option value='vt'>Vermont</option>
<option value='va'>Virginia</option>
<option value='wa'>Washington</option>
<option value='wv'>West Virginia</option>
<option value='wi'>Wisconsin</option>
<option value='wy'>Wyoming</option>
<option value='pr'>Puerto Rico</option>
</select>
</span>
<span data-tooltip='Choose a US water resource region'>
<select name='ushuc' id='ushuc' size='1' onchange='set_st(this);' >
<option value=''>Water Res. Region</option>
<option value='01'>01 New England</option>
<option value='02'>02 Mid Atlantic</option>
<option value='03'>03 South Atlantic-Gulf</option>
<option value='04'>04 Great Lakes</option>
<option value='05'>05 Ohio</option>
<option value='06'>06 Tennessee</option>
<option value='07'>07 Upper Mississippi</option>
<option value='08'>08 Lower Mississippi</option>
<option value='09'>09 Souris-Red-Rainy</option>
<option value='10'>10 Missouri</option>
<option value='11'>11 Arkansas-White-Red</option>
<option value='12'>12 Texas-Gulf</option>
<option value='13'>13 Rio Grande</option>
<option value='14'>14 Upper Colorado</option>
<option value='15'>15 Lower Colorado</option>
<option value='16'>16 Great Basin</option>
<option value='17'>17 Pacific Northwest</option>
<option value='18'>18 California</option>
<option value='19'>19 Alaska</option>
<option value='20'>20 Hawaii</option>
<option value='21'>21 Puerto Rico</option>
</select>
</span>
</div>
<div style="float: right; box-sizing: border-box;">
<form action="http://waterwatch.usgs.gov/download/?gt=map&ofmt=kmr&x=0&st=" id="down">
<input type="submit" value="Go to Google" / </form>
</div>
</td>
</tr>
<tr>
<td>
<div>
Canada:
<span data-tooltip='Choose a Canadian province'>
<select name='nus' id='nus' size='1' onchange='set_st(this);' >
<option value=''>Provinces</option>
<option value='zab'>Alberta</option>
<option value='zbc'>British Columbia</option>
<option value='zmb'>Manitoba</option>
<option value='znb'>New Brunswick</option>
<option value='znl'>Newfoundland and Labrador</option>
<option value='zns'>Nova Scotia</option>
<option value='znt'>Northwest Territories</option>
<option value='znu'>Nunavut</option>
<option value='zon'>Ontario</option>
<option value='zpe'>Prince Edward Island</option>
<option value='zqc'>Quebec</option>
<option value='zsk'>Saskatchewan</option>
<option value='zyt'>Yukon</option>
</select>
</span>
<span data-tooltip='Choose a Canadian river basin'>
<select name='nhuc' id='nhuc' size='1' onchange='set_st(this);' >
<option value=''>Canadian River Basins</option>
<option value='z01'>01 Maritime Provinces Drainage</option>
<option value='z02'>02 St.Lawrence River Drainage</option>
<option value='z03'>03 Northern Quebec Drainage</option>
<option value='z04'>04 Southwest Hudson Bay Drainage</option>
<option value='z05'>05 Nelson River Drainage</option>
<option value='z06'>06 Western Hudson Bay Drainage</option>
<option value='z07'>07 Great Slave Lake Drainage</option>
<option value='z08'>08 Pacific Drainage</option>
<option value='z09'>09 Yukon River Drainage</option>
<option value='z10'>10 Arctic Drainage</option>
<option value='z11'>11 Mississippi River Drainage</option>
</select>
</span>
</div>
<div style='margin-left: 10px; float: right;' data-tooltip="Click to view a map of specified region.">
<input name="go" value="Go" type="submit"/>
</div>
</td>
</tr>
</tbody>
</table>
</div>
</center>
</div>
</header>
<body>
<div class="center">
<div id="my-div">
<iframe src="http://watermonitor.gov/naww/index.php" id="my-iframe"></iframe>
</div>
</div>
<div class="legend">
<img name="legend" style="border: 0px" src="http://waterwatch.usgs.gov/new/images/map_legends/ptile_dot.gif" alt="map legend">
</div>
</body>
</html>
我的问题是关于id为“down”的按钮，我尝试在javascript中解决它的方法就在上面。
答案 0 :(得分：0)
试试这个：
获取选定的值
$( "#usst" ).val();
并设置srcattribüte
$（ “＃向下”）ATTR（ “SRC”，URL）;