How to store selected value of drop down list on local storage ?

I work or razor page asp.net core 7 . i face issue i can't store vlue of selected value option on local storage 

so please How to do that ?

<form id="FrmShelfLabelPrintrSetup" method="post">

    <div class="row">
        <div class="col-lg-12 col-12 row">
            <div class="col-md-3 col-lg-2">
                <label for="branch-selectlbl" style="margin-left:3px;font-size:15px;font-family: 'Open Sans', sans-serif;font-weight: bold;">Print Server</label>
          
                <select id="branch-select" asp-for="SelectedBranchId" name="selectbranchid" class="form-select" style="margin-left:3px;font-size:15px;font-family: 'Open Sans' , sans-serif;font-weight: bold;" onchange="toggleButtonVisibility()">
                    <option value="0">--Select--</option>
                    @foreach (var branches in Model.branches)
                    {
                        <option value="@branches.iBranchCode">@branches.vBranchDesc</option>
                    }
                </select>
               
            </div>
     
            <div class="col-md-3 col-lg-2">
                <br>
                <button  id="Searchtxt" type="submit" name="searchButton" value="search" asp-page-handler="Search" style="width:100px;margin-top:7px;" class="btn btn-primary">Search</button>
                <button id="createTxt" data-toggle="modal" data-target="#CreateshelflabelModal" style="width:100px;margin-top:7px;margin-left:7px;display:none;" class="btn btn-primary">Create</button>

            </div>

            
        </div>
    </div>
</form>

on page model what i do 

public class ShelfLabelPrinterSetUpModel : PageModel
{
     public async Task OnPostSearchAsync(string selectbranchid)
     {
        // how to store value of local storage here 
     }
}