Future Value Calculator

Public Class FVCalculator

    Private Function CalculateFV(pv As Decimal, rate As Decimal, periods As Integer) As Decimal
        ' Calculate future value using compound interest formula
        Return pv * Math.Pow(1 + (rate / 100), periods)
    End Function

    Private Sub btnCalculate_Click(sender As Object, e As EventArgs) Handles btnCalculate.Click
        Try
            ' Get input values
            Dim presentValue As Decimal = Decimal.Parse(txtPresentValue.Text)
            Dim interestRate As Decimal = Decimal.Parse(txtInterestRate.Text)
            Dim numPeriods As Integer = Integer.Parse(txtPeriods.Text)
            
            ' Calculate future value
            Dim futureValue As Decimal = CalculateFV(presentValue, interestRate, numPeriods)
            
            ' Display result with formatting
            lblResult.Text = futureValue.ToString("C2")
            
            ' Calculate total interest earned
            Dim totalInterest As Decimal = futureValue - presentValue
            lblInterest.Text = totalInterest.ToString("C2")
            
        Catch ex As Exception
            MessageBox.Show("Please enter valid numeric values", "Input Error", 
                            MessageBoxButtons.OK, MessageBoxIcon.Error)
        End Try
    End Sub

    Private Sub FVCalculator_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        ' Set default values
        txtPresentValue.Text = "1000"
        txtInterestRate.Text = "5"
        txtPeriods.Text = "5"
    End Sub
End Class

function calculateFV() {
    // Get input values
    const pv = parseFloat(document.getElementById('presentValue').value);
    const rate = parseFloat(document.getElementById('interestRate').value);
    const periods = parseInt(document.getElementById('periods').value);
    
    // Validate inputs
    if (isNaN(pv) || isNaN(rate) || isNaN(periods) || pv <= 0 || rate <= 0 || periods <= 0) {
        alert('Please enter valid positive numbers for all fields');
        return;
    }
    
    // Calculate future value
    const fv = pv * Math.pow(1 + (rate / 100), periods);
    const interest = fv - pv;
    
    // Format and display results
    document.getElementById('resultPV').textContent = formatCurrency(pv);
    document.getElementById('resultRate').textContent = rate + '%';
    document.getElementById('resultPeriods').textContent = periods;
    document.getElementById('resultFV').textContent = formatCurrency(fv);
    document.getElementById('resultInterest').textContent = formatCurrency(interest);
    
    // Show result container
    document.getElementById('resultContainer').style.display = 'block';
    
    // Generate growth chart
    generateGrowthChart(pv, rate, periods);
}

function formatCurrency(value) {
    return '$' + value.toFixed(2).replace(/\d(?=(\d{3})+\.)/g, '$&,');
}

function generateGrowthChart(pv, rate, periods) {
    const canvas = document.getElementById('growthChart');
    const ctx = canvas.getContext('2d');
    
    // Clear previous chart
    ctx.clearRect(0, 0, canvas.width, canvas.height);
    
    // Calculate data points
    const dataPoints = [];
    for (let i = 0; i <= periods; i++) {
        dataPoints.push(pv * Math.pow(1 + (rate / 100), i));
    }
    
    // Draw chart
    const maxValue = Math.max(...dataPoints);
    const chartHeight = canvas.height - 40;
    const chartWidth = canvas.width - 60;
    const barWidth = chartWidth / periods;
    
    // Draw axes
    ctx.strokeStyle = '#333';
    ctx.lineWidth = 1;
    ctx.beginPath();
    ctx.moveTo(40, 20);
    ctx.lineTo(40, chartHeight);
    ctx.lineTo(canvas.width - 20, chartHeight);
    ctx.stroke();
    
    // Draw bars and labels
    ctx.fillStyle = '#5c6bc0';
    ctx.font = '12px Poppins';
    ctx.textAlign = 'center';
    
    for (let i = 0; i < dataPoints.length; i++) {
        const barHeight = (dataPoints[i] / maxValue) * (chartHeight - 30);
        const x = 40 + (i * barWidth) + (barWidth / 2);
        const y = chartHeight - barHeight;
        
        // Draw bar
        ctx.fillRect(x - (barWidth * 0.8 / 2), y, barWidth * 0.8, barHeight);
        
        // Draw value label
        ctx.fillStyle = '#333';
        ctx.fillText('Y' + i, x, chartHeight + 20);
        
        // Draw value at top
        if (i > 0) {
            ctx.fillText(formatCurrency(dataPoints[i]), x, y - 5);
        }
        
        ctx.fillStyle = '#5c6bc0';
    }
    
    // Draw chart title
    ctx.fillStyle = '#333';
    ctx.font = 'bold 14px Poppins';
    ctx.textAlign = 'center';
    ctx.fillText('Investment Growth Over Time', canvas.width / 2, 15);
    
    // Show chart container
    document.getElementById('chartContainer').style.display = 'block';
}

function openTab(evt, tabName) {
    // Hide all tab contents
    const tabContents = document.getElementsByClassName("tab-content");
    for (let i = 0; i < tabContents.length; i++) {
        tabContents[i].classList.remove("active");
    }
    
    // Remove active class from all buttons
    const tabButtons = document.getElementsByClassName("tab-btn");
    for (let i = 0; i < tabButtons.length; i++) {
        tabButtons[i].classList.remove("active");
    }
    
    // Show current tab and set button as active
    document.getElementById(tabName).classList.add("active");
    evt.currentTarget.classList.add("active");
}