find the server side code in index.razor page below

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@page "/"

@inject HttpClient Http
<button @onclick="CallJsMethod">Call JavaScript method</button>

@code {
    [Inject] IJSRuntime jsRuntime { get; set; }

    private async Task CallJsMethod()
    {
        await jsRuntime.InvokeVoidAsync("MyJsFunction", "some data");
    }
}
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find the client side(javascript) in index.html page below

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<script>
        function MyJsFunction(data) {
            var formData = new FormData();
            formData.append("file", data);

            var ajax = new XMLHttpRequest();
            ajax.open("POST", "/api/SampleData/Save");
            ajax.onload = function (e) {
                console.log("File uploaded successfully.");
            };
            ajax.onerror = function (e) {
                console.error("Error occurred while uploading the file.");
            };
            ajax.upload.addEventListener("progress", handleProgress); 
            function handleProgress(e) {
                if (e.lengthComputable) {
                    var percentComplete = (e.loaded / e.total) * 100;
                    console.log(percentComplete + "% uploaded.");
                }
            }
            ajax.send(formData);
        }

    </script>
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