JS category subcategory - hide value from subcat when category is selected [closed]

I got [category] and [subcategory]. If user select [category-option(1)], then hide some value from [subcategory].

This is from school project where we want to have two select options for uploading files, but in some classes like (5th grade some subjects are different from 6th grade). So I thought of this simple idea. Store all classes/subjects in HTML, then if user clicks on 5th grade hide some subjects that they don't learn. But if user clicks 7gr to display subjects that are learned there.

<div class="input-group mb-3">      <select class="custom-select" id="category" name="category" label="x">          <optgroup label="Изберете клас" id="category" name="category">                <option value="5">5 клас</option>              <option value="6">6 клас</option>              <option value="7">7 клас</option>              <option value="8">8 клас</option>              <option value="9">9 клас</option>              <option value="10">10 клас</option>              <option value="11">11 клас</option>              <option value="12">12 клас</option>          </optgroup>      </select>      <select class="custom-select" id="sub_category" name="sub_category">          <optgroup label="Изберете Предмет" id="sub_category" name="sub_category">              <option value="ФИЗИКА">ФИЗИКА</option>               <option value="БИОЛОГИЯ">БИОЛОГИЯ</option>              <option value="МАТЕМАТИКА">МАТЕМАТИКА</option>               <option value="ИСТОРИЯ">ИСТОРИЯ</option>              <option value="ХИМИЯ">ХИМИЯ</option>               <option value="АНГЛИЙСКИ">АНГЛИЙСКИ</option>              <option value="ИНФОРМАТИКА">ИНФОРМАТИКА</option>               <option value="ТЕХНОЛОГИЙ">ТЕХНОЛОГИЙ</option>          </optgroup>      </select>      <div class="input-group-append">          <button class="btn btn-success" type="submit">Качи</button>      </div>        </div>  

https://stackoverflow.com/questions/66839101/js-category-subcategory-hide-value-from-subcat-when-category-is-selected March 28, 2021 at 02:55PM