chartjs

Chart.js Quick Charting Skill

Create beautiful, responsive charts in minutes with Chart.js - the simple yet flexible JavaScript charting library.

When to Use This Skill

Use Chart.js when you need:

Quick implementation - Up and running in minutes
Simple charts - Line, bar, pie, doughnut, radar charts
Minimal configuration - Sensible defaults that work out of the box
Small projects - Lightweight library (60KB gzipped)
Responsive charts - Mobile-friendly by default
No dependencies - Standalone library

Avoid when:

Complex customization needed (use D3.js)
3D charts required (use Plotly)
Advanced scientific visualizations needed (use Plotly)
Large datasets >10k points (use Plotly with WebGL)

Core Capabilities

Basic Line Chart

<!DOCTYPE html> <html> <head> <script src="https://cdn.jsdelivr.net/npm/chart.js"></script> </head> <body> <canvas id="myChart" width="400" height="200"></canvas> <script> const ctx = document.getElementById('myChart').getContext('2d'); const myChart = new Chart(ctx, { type: 'line', data: { labels: ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun'], datasets: [{ label: 'Sales 2024', data: [12, 19, 3, 5, 2, 3], borderColor: 'rgb(75, 192, 192)', backgroundColor: 'rgba(75, 192, 192, 0.2)', tension: 0.1 }] }, options: { responsive: true, plugins: { title: { display: true, text: 'Monthly Sales' } } } }); </script> </body> </html>

Bar Chart

const ctx = document.getElementById('barChart').getContext('2d'); const barChart = new Chart(ctx, { type: 'bar', data: { labels: ['Red', 'Blue', 'Yellow', 'Green', 'Purple', 'Orange'], datasets: [{ label: 'Votes', data: [12, 19, 3, 5, 2, 3], backgroundColor: [ 'rgba(255, 99, 132, 0.6)', 'rgba(54, 162, 235, 0.6)', 'rgba(255, 206, 86, 0.6)', 'rgba(75, 192, 192, 0.6)', 'rgba(153, 102, 255, 0.6)', 'rgba(255, 159, 64, 0.6)' ], borderColor: [ 'rgba(255, 99, 132, 1)', 'rgba(54, 162, 235, 1)', 'rgba(255, 206, 86, 1)', 'rgba(75, 192, 192, 1)', 'rgba(153, 102, 255, 1)', 'rgba(255, 159, 64, 1)' ], borderWidth: 1 }] }, options: { responsive: true, scales: { y: { beginAtZero: true } } } });

Pie/Doughnut Chart

const ctx = document.getElementById('pieChart').getContext('2d'); const pieChart = new Chart(ctx, { type: 'pie', // or 'doughnut' data: { labels: ['Desktop', 'Mobile', 'Tablet'], datasets: [{ label: 'Device Usage', data: [55, 35, 10], backgroundColor: [ 'rgb(255, 99, 132)', 'rgb(54, 162, 235)', 'rgb(255, 205, 86)' ], hoverOffset: 4 }] }, options: { responsive: true, plugins: { legend: { position: 'top', }, title: { display: true, text: 'Device Usage Statistics' } } } });

Complete Examples

Example 1: Multi-Dataset Line Chart

<!DOCTYPE html> <html> <head> <script src="https://cdn.jsdelivr.net/npm/chart.js"></script> <style> .chart-container { position: relative; height: 400px; width: 80%; margin: auto; } </style> </head> <body> <div class="chart-container"> <canvas id="multiLineChart"></canvas> </div> <script> const ctx = document.getElementById('multiLineChart').getContext('2d'); const chart = new Chart(ctx, { type: 'line', data: { labels: ['Week 1', 'Week 2', 'Week 3', 'Week 4'], datasets: [ { label: 'Product A', data: [30, 50, 45, 60], borderColor: 'rgb(255, 99, 132)', backgroundColor: 'rgba(255, 99, 132, 0.1)', tension: 0.4 }, { label: 'Product B', data: [20, 40, 55, 50], borderColor: 'rgb(54, 162, 235)', backgroundColor: 'rgba(54, 162, 235, 0.1)', tension: 0.4 }, { label: 'Product C', data: [40, 30, 35, 55], borderColor: 'rgb(75, 192, 192)', backgroundColor: 'rgba(75, 192, 192, 0.1)', tension: 0.4 } ] }, options: { responsive: true, maintainAspectRatio: false, interaction: { mode: 'index', intersect: false, }, plugins: { title: { display: true, text: 'Product Sales Comparison' }, legend: { display: true, position: 'top' } }, scales: { y: { beginAtZero: true, title: { display: true, text: 'Sales (units)' } }, x: { title: { display: true, text: 'Time Period' } } } } }); </script> </body> </html>

Example 2: Stacked Bar Chart

const ctx = document.getElementById('stackedBar').getContext('2d'); const stackedChart = new Chart(ctx, { type: 'bar', data: { labels: ['Q1', 'Q2', 'Q3', 'Q4'], datasets: [ { label: 'Revenue', data: [100, 120, 115, 134], backgroundColor: 'rgba(75, 192, 192, 0.7)', }, { label: 'Costs', data: [60, 70, 65, 80], backgroundColor: 'rgba(255, 99, 132, 0.7)', }, { label: 'Profit', data: [40, 50, 50, 54], backgroundColor: 'rgba(54, 162, 235, 0.7)', } ] }, options: { responsive: true, scales: { x: { stacked: true, }, y: { stacked: true, beginAtZero: true } }, plugins: { title: { display: true, text: 'Quarterly Financial Overview' } } } });

Example 3: Radar Chart

const ctx = document.getElementById('radarChart').getContext('2d'); const radarChart = new Chart(ctx, { type: 'radar', data: { labels: ['Speed', 'Reliability', 'Comfort', 'Safety', 'Efficiency'], datasets: [ { label: 'Vehicle A', data: [85, 90, 70, 95, 80], backgroundColor: 'rgba(255, 99, 132, 0.2)', borderColor: 'rgb(255, 99, 132)', pointBackgroundColor: 'rgb(255, 99, 132)', }, { label: 'Vehicle B', data: [75, 85, 90, 85, 90], backgroundColor: 'rgba(54, 162, 235, 0.2)', borderColor: 'rgb(54, 162, 235)', pointBackgroundColor: 'rgb(54, 162, 235)', } ] }, options: { responsive: true, scales: { r: { beginAtZero: true, max: 100 } }, plugins: { title: { display: true, text: 'Vehicle Comparison' } } } });

Example 4: Loading Data from CSV

// Using Fetch API to load CSV fetch('../data/sales.csv') .then(response => response.text()) .then(csvText => { const lines = csvText.split('\n'); const headers = lines[0].split(',');

const labels = [];
const data = [];

for (let i = 1; i &#x3C; lines.length; i++) {
  const values = lines[i].split(',');
  labels.push(values[0]);
  data.push(parseFloat(values[1]));
}

const ctx = document.getElementById('csvChart').getContext('2d');
new Chart(ctx, {
  type: 'line',
  data: {
    labels: labels,
    datasets: [{
      label: 'Sales Data',
      data: data,
      borderColor: 'rgb(75, 192, 192)',
      tension: 0.1
    }]
  },
  options: {
    responsive: true
  }
});

});

Example 5: Real-Time Updating Chart

const ctx = document.getElementById('realtimeChart').getContext('2d'); const chart = new Chart(ctx, { type: 'line', data: { labels: [], datasets: [{ label: 'Real-time Data', data: [], borderColor: 'rgb(75, 192, 192)', tension: 0.1 }] }, options: { responsive: true, scales: { x: { display: true }, y: { beginAtZero: true } }, animation: { duration: 0 // Disable animation for real-time } } });

// Update every second let dataPoint = 0; setInterval(() => { const now = new Date(); const timeLabel = now.getHours() + ':' + now.getMinutes() + ':' + now.getSeconds();

chart.data.labels.push(timeLabel); chart.data.datasets[0].data.push(Math.random() * 100);

// Keep only last 20 points if (chart.data.labels.length > 20) { chart.data.labels.shift(); chart.data.datasets[0].data.shift(); }

chart.update(); }, 1000);

Example 6: Mixed Chart Types

const ctx = document.getElementById('mixedChart').getContext('2d'); const mixedChart = new Chart(ctx, { data: { labels: ['Jan', 'Feb', 'Mar', 'Apr', 'May'], datasets: [ { type: 'bar', label: 'Sales', data: [50, 60, 70, 80, 90], backgroundColor: 'rgba(54, 162, 235, 0.7)', }, { type: 'line', label: 'Target', data: [55, 65, 75, 85, 95], borderColor: 'rgb(255, 99, 132)', fill: false } ] }, options: { responsive: true, plugins: { title: { display: true, text: 'Sales vs Target' } } } });

Best Practices

Use Responsive Containers

options: { responsive: true, maintainAspectRatio: false }

Destroy Charts Before Recreating

let myChart;

function createChart(data) { // Destroy existing chart if (myChart) { myChart.destroy(); }

const ctx = document.getElementById('myChart').getContext('2d'); myChart = new Chart(ctx, { type: 'line', data: data }); }

Use Plugins for Extended Functionality

// Example: Chart.js Data Labels Plugin import ChartDataLabels from 'chartjs-plugin-datalabels';

const chart = new Chart(ctx, { plugins: [ChartDataLabels], data: {...}, options: { plugins: { datalabels: { color: '#fff', display: true } } } });

Optimize for Performance

options: { // Disable animations for large datasets animation: { duration: 0 }, // Use decimation for large datasets parsing: false, normalized: true }

Available Chart Types

Line - Trend analysis, time series
Bar - Comparisons, categorical data
Pie - Proportions, percentages
Doughnut - Like pie, with center hole
Radar - Multivariate data
Polar Area - Similar to pie with variable radii
Bubble - 3-dimensional data (x, y, size)
Scatter - Correlation analysis

Common Customizations

Custom Colors

const colors = [ 'rgba(255, 99, 132, 0.7)', 'rgba(54, 162, 235, 0.7)', 'rgba(255, 206, 86, 0.7)', 'rgba(75, 192, 192, 0.7)', 'rgba(153, 102, 255, 0.7)' ];

Custom Tooltips

options: { plugins: { tooltip: { callbacks: { label: function(context) { let label = context.dataset.label || ''; if (label) { label += ': '; } label += '$' + context.parsed.y.toFixed(2); return label; } } } } }

Custom Legends

options: { plugins: { legend: { position: 'bottom', labels: { font: { size: 14 }, usePointStyle: true } } } }

Installation

CDN (Quick Start)

NPM

npm install chart.js

import Chart from 'chart.js/auto';

ES Modules

const ctx = document.getElementById('myChart'); new Chart(ctx, {...}); </script>

Popular Plugins

Chart.js Zoom Plugin

npm install chartjs-plugin-zoom

import zoomPlugin from 'chartjs-plugin-zoom'; Chart.register(zoomPlugin);

options: { plugins: { zoom: { zoom: { wheel: { enabled: true }, pinch: { enabled: true }, mode: 'xy' } } } }

Chart.js Annotation Plugin

npm install chartjs-plugin-annotation

Chart.js Data Labels

npm install chartjs-plugin-datalabels

Integration Examples

With React

import { useEffect, useRef } from 'react'; import Chart from 'chart.js/auto';

function ChartComponent({ data }) { const chartRef = useRef(null); const chartInstance = useRef(null);

useEffect(() => { if (chartInstance.current) { chartInstance.current.destroy(); }

const ctx = chartRef.current.getContext('2d');
chartInstance.current = new Chart(ctx, {
  type: 'line',
  data: data,
  options: { responsive: true }
});

return () => {
  if (chartInstance.current) {
    chartInstance.current.destroy();
  }
};

}, [data]);

return <canvas ref={chartRef} />; }

With Vue

export default { props: ['chartData'], mounted() { this.renderChart(); }, methods: { renderChart() { const ctx = this.$refs.chartCanvas.getContext('2d'); new Chart(ctx, { type: 'bar', data: this.chartData, options: { responsive: true } }); } } }; </script>

Resources

Official Docs: https://www.chartjs.org/docs/latest/
Samples: https://www.chartjs.org/docs/latest/samples/
GitHub: https://github.com/chartjs/Chart.js
Community: https://github.com/chartjs/awesome

Performance Tips

Disable animations for large datasets
Use decimation to reduce data points
Limit updates - batch chart updates
Destroy unused charts - free memory
Use canvas size wisely - larger canvas = slower rendering

Use this skill for quick, simple charts that look great with minimal configuration!

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