javascript - GetElementById of ASP.NET Control keeps returning 'null' -

-

i'm desperate having spent on hour trying troubleshoot this. trying access node in dom created asp.net control. i'm using same id , can see match when looking @ html source code after page has rendered. here's [modified according suggestions, still not working] code:

asp.net header

<asp:content id="headercontent" runat="server" contentplaceholderid="headcontent">     <script type="text/javascript">     $(document).ready(         var el = document.getelementbyid('<%= txtbox.clientid %>');         el.onchange = alert('test!!');     )     </script> </asp:content>

asp.net body

<asp:textbox id="txtbox" runat="server"></asp:textbox>

resulting javascript & html above

<script type="text/javascript"> $(document).ready(     var el = document.getelementbyid('maincontent_txtbox');     el.onchange = alert('test!!'); ) </script> ... <textarea name="ctl00$maincontent$txtbox" id="maincontent_txtbox"></textarea>

i can assume script loading before control id has been resolved, yet when @ timeline chrome's "inspect element" feature, appears not case. when created regular textarea box test , implement identical code (different id of course), alert box fires.

what on earth missing here? driving me crazy >.<

edit: wierd code works, on initial page load; firing onload rather onchange. jquery says .ready doesn't work apparently. ugh!!

$(document).ready(function() {     document.getelementbyid('<%= txtbox.clientid %>').onchange = alert('working!'); })

assuming rendered markup appear in order, problem element doesn't yet exist @ time javascript attempting locate it.

either move js below element (preferably right @ end of body) or wrap in jquery's document ready event handler.

update:

in response edits, you're there (as others have mentioned) need assign function onchange event, not return result of alert(). this:

$(document).ready(function() {   // might use jquery attach event since you're using   //  document ready event.   $('#<%= txtbox.clientid %>').change(function() {     alert('working!');   }); });

by writing onchange = alert('working');, asking javascript assign result of alert() method onchange property. that's why executing on page load, never in response onchange event (because hadn't assigned function run onchange).


Comments

Post a Comment

Popular posts from this blog

c# - How to set Z index when using WPF DrawingContext? -

-
how set z-index drawing object when using drawingcontext.drawxxx() methods? the object drawn last have higher z index. can't change index of drawn objects. way draw in order. if using wpf (as placed tag), can use, example, canvas control. create shapes need like polyline obj = new polyline(); //... // ... set properties of obj and add them canvas uielementcollection: yourcanvasname.children.add(obj); //or yourcanvasname.children.insert(i, obj); first items of collection have higher z index. advantages in way: no need redraw on window changes, can anytime move objects , change order.
Read more

razor - Is this a bug in WebMatrix PageData? -

-
i think may have found bug in webmatrix's pagedata, not sure. concerns how pass data partial page calling page. in webmatrix documentation (tutorials, e.g. " 3 - creating consistent look ", , example code), pagedata recommended mechanism pass data between pages (e.g. content page layout page, or partial page). however have found not work other way, pass data partial page calling page. modifying or adding entries in pagedata in partial page, not seem calling page. cutting right down simplest possible example, in test page may have this: @{ pagedata["test"] = "initial entry"; } <p>before calling partial page, test value @pagedata["test"]</p> @renderpage("_testpartial.cshtml") <p>after returning calling page, test value @pagedata["test"]</p> and in _testpartial.cshtml page might have this: @{ pagedata["test"] = "modified entry"; } <p>in partial page...
Read more

visual c++ - Using relative values in array sorting ( asm ) -

-
i need sort through array , sort each individual row in array in ascending order. doesn't seem going (surprise!) keep getting hit 2 errors: a2101: cannot add 2 relocatable labels , a2026: constant expected here's sort, makes sense me, think i'm still trying implement high-lvl language techniqes assembly. there way around not being able use relative values? (the array 7 rows 9 columns, btw). mov cx, 7; cx = number of rows outer: ; outer loop walk through rows push cx mov cx, 9 mov row, cx ;rows middle: ; middle-loop walk through columns push cx sub cx, 1 ;cx = cx-1 mov column, cx ;columns inner: ;inner loop - compare , exchange column values cmp marray[row*9 + column], marray[row*9 + column+1] xchg marray[row*9 + column+1], marray[row*9 + column] ; compare , exchange values marray table inc column loop inner pop cx loop mid...
Read more