Chart.js Usage

To create charts using Chart.js, you need to initialize the Chart class and pass in the chart node:

HTML Canvas code, where the chart will be displayed:

<canvas id="myChart" width="400" height="400"></canvas>

Get the node in different ways:

Initialization Methods

// Any of the following methods can be used
const ctx = document.getElementById('myChart');  // Get the node
const ctx = document.getElementById('myChart').getContext('2d');  // getContext() method returns the canvas context
const ctx = $('#myChart'); // jQuery get
const ctx = 'myChart'; // Pass in the node ID

After obtaining the element node with the above code, we can create our own chart type.

The following example creates a simple line chart:

Example

const ctx = document.getElementById('myChart');
const labels = ['January', 'February', 'March', 'April', 'May', 'June', 'July'];  // Set labels on the X-axis
const data = {
  labels: labels,
  datasets: [{
    label: 'My First Line Chart',
    data: [65, 59, 80, 81, 56, 55, 40],
    fill: false,
    borderColor: 'rgb(75, 192, 192)', // Set the line color
    tension: 0.1
  }]
};
const config = {
  type: 'line', // Set the chart type
  data: data,
};
const myChart = new Chart(ctx, config);

The output result of the above example is:

The following example creates a bar chart showing votes with different colors.

Example

const ctx = document.getElementById('myChart');
const myChart = new Chart(ctx, {
    type: 'bar',
    data: {
        labels: ['Red', 'Blue', 'Yellow', 'Green', 'Purple', 'Orange'],
        datasets: [{
            label: '# of Votes',
            data: [12, 19, 3, 5, 2, 3],
            backgroundColor: [
                'rgba(255, 99, 132, 0.2)',
                'rgba(54, 162, 235, 0.2)',
                'rgba(255, 206, 86, 0.2)',
                'rgba(75, 192, 192, 0.2)',
                'rgba(153, 102, 255, 0.2)',
                'rgba(255, 159, 64, 0.2)'
            ],
            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: {
        scales: {
            y: {
                beginAtZero: true
            }
        }
    }
});

The output result of the above example is:

Configuration Object Structure

The common structure of the configuration object is as follows:

const config = {
  type: 'line',
  data: {},
  options: {},
  plugins: []
}

Parameter Explanation:

• type -- Specifies the type of chart
• data -- The dataset displayed in the chart
• options -- Optional configurations, which vary for different types of charts
• plugins -- Plugins