how to add javascript or js in asp.net

from your solution Explorer right click Add "New folder"
then rename "Script" then right click the created Folder name "Script"
then add -> New Item then pop up will show then choose "Web" and choose again name "JScript1.js" then place your code in JScript1.js

don't forget to reference your script to masterpage oki

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if this will help you
thanks

in your design page after closing of title tag you can use java script like this

<script type="text/javascript" language="javascript">
your code goes here...
</script>

and for using jscript go to your solution explorer window and add new item in that you can select jscript and you can use it in the web page.