Restrict Category Axis to Bottom in Chart.js Without Empty Labels

When Working With Chart.js, Category Axis Placement Can Be Frustrating

When using Chart.js, ensuring that the category axis (x-axis) appears exactly at the bottom can be a challenge, especially when working with multiple axes. A common issue is that the axis refuses to align without inserting unnecessary empty labels.

Rather than resorting to hacks like adding empty labels, I’ll explain how to properly configure the category axis placement using built-in Chart.js options.

How Chart.js Handles Axes

Charts rely on axes to properly display data. In Chart.js, the x-axis typically represents categories (labels), while the y-axis shows numerical values.

A category axis is defined by a list of labels, determining where data points appear horizontally. The challenge comes when you want the category axis to stay strictly at the bottom, especially in multi-axis setups.

Each axis in Chart.js has a position property defining where it should be placed. By default, an x-axis can be positioned at “top”, “bottom”, or “center”. While setting it to “bottom” should place it there, certain configurations can cause misalignment.

Why Empty Labels Are a Bad Idea

A common mistake is adding empty strings ("") to the labels array to force placement. This workaround leads to several problems:

• Unnecessary whitespace: Empty labels create unwanted space, making the chart messy.
• Poor readability: Unlabeled gaps confuse users, making the chart harder to understand.
• Code clutter: Manually inserting empty labels makes the chart difficult to maintain, especially when working with dynamic data.

Instead of using empty labels, let’s go over the correct way to keep the category axis at the bottom.

Setting the Category Axis at the Bottom Correctly

Follow these steps to properly lock the category axis at the bottom:

1. Set the position Property

Chart.js allows direct control over axis placement using the position property. If your axis appears elsewhere, explicitly setting it ensures correct placement.

const config = {
  type: 'bar',
  data: {
    labels: ['Jan', 'Feb', 'Mar', 'Apr', 'May'],
    datasets: [{
      label: 'Sales',
      data: [30, 50, 40, 70, 60]
    }]
  },
  options: {
    scales: {
      x: {
        position: 'bottom'
      }
    }
  }
};

new Chart(document.getElementById('myChart'), config);

With this setup, the category axis remains at the bottom without requiring empty labels.

2. Check Grid Lines and Ticks

Some placement issues arise due to the default grid and tick settings. If your category axis still shifts, adjust these options:

scales: {
  x: {
    position: 'bottom',
    grid: {
      display: false // Hides grid lines affecting alignment
    },
    ticks: {
      autoSkip: false, // Prevents Chart.js from skipping labels
      maxRotation: 0,  // Keeps labels horizontal
      align: 'center'
    }
  }
}

This ensures that the labels remain properly spaced without manipulation.

3. Use Custom Category Labels Where Needed

If your data needs specific formatting, opt for dynamic label formatting rather than inserting placeholders.

scales: {
  x: {
    type: 'category',
    labels: ['Q1', 'Q2', 'Q3', 'Q4'],
    position: 'bottom'
  }
}

This keeps the configuration clean while ensuring that the labels align naturally.

Tips for a Well-Organized Chart

Beyond correct axis placement, here are some best practices for maintaining a clean chart:

• Rotate Labels if Needed: If labels overlap, use maxRotation and minRotation to improve spacing.
• Keep Labels Clear: Avoid redundancy—use “Jan”, “Feb” instead of “Jan 2024”, “Feb 2024” if the year is implied.
• Ensure Labels Align With Data: Labels should correspond intuitively with data points, avoiding artificial manipulations.

Example Configuration Without Empty Labels

Here’s a full implementation ensuring category axis placement at the bottom:

const ctx = document.getElementById('myChart').getContext('2d');
new Chart(ctx, {
  type: 'line',
  data: {
    labels: ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday'],
    datasets: [{
      label: 'Visitors',
      data: [12, 19, 3, 5, 2],
      borderColor: 'blue',
      fill: false
    }]
  },
  options: {
    scales: {
      x: {
        position: 'bottom',
        grid: {
          display: false
        }
      }
    }
  }
});

This ensures the category axis stays where it belongs—cleanly at the bottom.

Why This Approach is Better

• No Unwanted Whitespace: Keeps charts clean and professional.
• Better Data Accuracy: No misleading gaps between labels.
• Easier Maintenance: Dynamic updates happen seamlessly.

By avoiding empty labels and properly configuring Chart.js, you can create well-structured, visually clear charts. Have you been struggling with misplaced category axes? Try these methods, and let me know your thoughts in the comments.