How do you call JavaScript from C# code in Blazor (JS interop), and when is it necessary?

IJSRuntime.InvokeAsync<T>("functionName", args) calls a JavaScript function from C# and awaits its result, necessary for accessing browser APIs Blazor doesn't wrap natively (like localStorage, certain DOM APIs, or existing third-party JS libraries like chart rendering libraries) that don't have a direct Blazor equivalent.

@inject IJSRuntime JS

<button @onclick="ShowAlert">Alert</button>

@code {
    private async Task ShowAlert() {
        await JS.InvokeVoidAsync("alert", "Hello from Blazor!");
    }
}