如何用JavaScript实现表单提交时生成用户输入的奖牌数据表格及柱状图

Alright, let's build this from scratch. I'll provide a complete, self-contained implementation using vanilla HTML, CSS, and JavaScript—no external libraries needed, so it's easy to integrate anywhere.

Step 1: The HTML Form & Chart Container #

First, we'll create a simple form to capture country names and their medal counts, plus a container where the bar chart will render.

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Champions League Medals Bar Chart</title>
    <style>
        .chart-container {
            margin-top: 30px;
            display: flex;
            align-items: flex-end;
            height: 400px;
            gap: 20px;
            padding: 20px;
            border-bottom: 2px solid #333;
            border-left: 2px solid #333;
        }
        .bar {
            flex: 1;
            background-color: #2563eb;
            position: relative;
            border-radius: 4px 4px 0 0;
            transition: height 0.3s ease;
        }
        .bar-label {
            position: absolute;
            bottom: -25px;
            width: 100%;
            text-align: center;
            font-size: 14px;
            color: #333;
        }
        .bar-value {
            position: absolute;
            top: -25px;
            width: 100%;
            text-align: center;
            font-weight: bold;
            color: #2563eb;
        }
        form {
            display: flex;
            gap: 10px;
            align-items: center;
            margin-bottom: 20px;
        }
        input {
            padding: 8px 12px;
            border: 1px solid #ddd;
            border-radius: 4px;
        }
        button {
            padding: 8px 16px;
            background-color: #2563eb;
            color: white;
            border: none;
            border-radius: 4px;
            cursor: pointer;
        }
        button:hover {
            background-color: #1d4ed8;
        }
    </style>
</head>
<body>
    <form id="medalForm">
        <input type="text" id="countryName" placeholder="Enter country name" required>
        <input type="number" id="medalCount" placeholder="Medal count" min="1" required>
        <button type="submit">Add to Chart</button>
    </form>

    <div id="chartContainer" class="chart-container"></div>

    <script>
        // JavaScript logic goes here
    </script>
</body>
</html>

Step 2: JavaScript Logic to Generate the Bar Chart #

Now let's add the JavaScript that handles form submission, stores the data, and renders the chart dynamically.

Add this inside the <script> tag:

// Store our medal data in an array
const medalData = [];

// Get references to DOM elements
const form = document.getElementById('medalForm');
const chartContainer = document.getElementById('chartContainer');

// Handle form submission
form.addEventListener('submit', function(e) {
    // Prevent default form reload
    e.preventDefault();

    // Get input values
    const country = document.getElementById('countryName').value.trim();
    const count = parseInt(document.getElementById('medalCount').value);

    // Validate input (basic check)
    if (!country || isNaN(count) || count < 1) {
        alert('Please enter a valid country name and positive medal count!');
        return;
    }

    // Add data to our array
    medalData.push({ country, count });

    // Reset the form
    form.reset();

    // Re-render the chart
    renderChart();
});

// Function to render the bar chart
function renderChart() {
    // Clear existing chart
    chartContainer.innerHTML = '';

    // If no data, show a message
    if (medalData.length === 0) {
        chartContainer.innerHTML = '<p style="width: 100%; text-align: center; color: #666;">No data added yet. Enter a country and medal count to start!</p>';
        return;
    }

    // Find the maximum medal count to scale our bars
    const maxCount = Math.max(...medalData.map(item => item.count));

    // Create a bar for each data point
    medalData.forEach(item => {
        // Calculate bar height relative to max count (so bars fit in the container)
        const barHeight = (item.count / maxCount) * 100;

        // Create bar element
        const bar = document.createElement('div');
        bar.className = 'bar';
        bar.style.height = `${barHeight}%`;

        // Add country label
        const label = document.createElement('div');
        label.className = 'bar-label';
        label.textContent = item.country;
        bar.appendChild(label);

        // Add medal count value
        const value = document.createElement('div');
        value.className = 'bar-value';
        value.textContent = item.count;
        bar.appendChild(value);

        // Add bar to chart container
        chartContainer.appendChild(bar);
    });
}

// Initialize the chart with empty state
renderChart();

How It Works #

Let's break down the key parts:

• Form Handling: We listen for the form's submit event, stop the page from reloading, grab the input values, and validate them to ensure we're getting valid data.
• Data Storage: We keep track of all submitted entries in an array (medalData), so we can build the chart with all accumulated data each time.
• Dynamic Chart Rendering: The renderChart() function does the heavy lifting:
  • It clears any existing bars to start fresh.
  • It calculates the maximum medal count to scale all bars proportionally (so the tallest bar fills the container height).
  • For each entry, it creates a bar div with a height based on the scaled value, then adds the country label and medal count on top/bottom.
  • It appends each bar to the chart container.

Customization Tips #

• Change Colors: Modify the background-color values in the CSS to match your preferred color scheme.
• Adjust Chart Size: Tweak the height of .chart-container in the CSS to make the chart taller/shorter.
• Add Animations: The existing CSS has a transition on the bar height—you can expand this with more animations if you want.
• Edit Validation: Add stricter checks (like preventing duplicate country entries) by adding a check in the form submission handler before pushing to medalData.

内容的提问来源于stack exchange，提问作者Nayana Chandran