How to get which URL the request is being made to?

Question

JavaScript

Hello, I have this piece of code

<div class="mpei-galaktika-group-form-control"><input name="ctl00$ctl30$g_f0649160_e72e_4671_a36b_743021868df5$ctl03" type="text" placeholder="Введите название группы"><input type="submit" name="ctl00$ctl30$g_f0649160_e72e_4671_a36b_743021868df5$ctl04" value=" >> " onclick="javascript:WebForm_DoPostBackWithOptions(new WebForm_PostBackOptions(&quot;ctl00$ctl30$g_f0649160_e72e_4671_a36b_743021868df5$ctl04&quot;, &quot;&quot;, true, &quot;&quot;, &quot;&quot;, false, false))"></div>

When submit is clicked, the value from the input is taken, after which it is redirected to the page where values ​​have already been substituted that do not match what was entered in the input. How to find out exactly where the request is being made in order to get GET parameters?