export function error(){
    alert('oops, an error');
}

var module = await JS.InvokeAsync<IJSObjectReference>("import", "./Panel.razor.js");
await module.InvokeVoidAsync("error");

Pages/Panel.razor
Pages/Panel.razor.js
Pages/Panel.razor.css

_module = await JS.InvokeAsync<IJSObjectReference>("import", "./_content/RazorClassLibrary/componentName.razor.js");

export function showPrompt(message) {
  return prompt(message, 'Type anything here');
}

@page "/call-js-example-6"
@implements IAsyncDisposable
@inject IJSRuntime JS

<h1>Call JS Example 6</h1>

<p>
    <button @onclick="TriggerPrompt">Trigger browser window prompt</button>
</p>

<p>
    @result
</p>

@code {
    private IJSObjectReference? module;
    private string? result;

    protected override async Task OnAfterRenderAsync(bool firstRender)
    {
        if (firstRender)
        {
            module = await JS.InvokeAsync<IJSObjectReference>("import", 
                "./scripts.js");
        }
    }

    private async Task TriggerPrompt()
    {
        result = await Prompt("Provide some text");
    }

    public async ValueTask<string?> Prompt(string message) =>
        module is not null ? 
            await module.InvokeAsync<string>("showPrompt", message) : null;

    async ValueTask IAsyncDisposable.DisposeAsync()
    {
        if (module is not null)
        {
            await module.DisposeAsync();
        }
    }
}

<location path="elmah.axd">
    <system.web>
        <authorization>
            <allow roles="Admin" />
            <deny users="*" />
        </authorization>
    </system.web>
</location>