How to compare one value to another in chartJS - chart.js

Question

I have been working on a broadband management website.I want to show the user how much data he/she has used.For example if the total data they have in their name is 300GB.If they have used 150GB the remaining is 150GB right?.How to do i visualize this using a doughnut chart,Using ChartJS.
I have some code going but im not sure how to accomplish this please help me out
var ctx = document.getElementById('myChart').getContext('2d');
var constdata=document.getElementById("constantdata").textContent;
var data=document.getElementById("data").textContent;
console.log(data);
var chart = new Chart(ctx, {
// The type of chart we want to create
type: 'doughnut',
// The data for our dataset
data: {
datasets: [{
label: 'My First dataset',
backgroundColor: ['red','green'],
borderColor: 'rgb(255, 99, 132)',
data: [300,150] //300 being the total data,150 being the data used
}]
},
// Configuration options go here
options: {}
But the above code isnt working out.Assume a doughnut chart,If the used data is 150GB(out of 300).The doughnut
chart must be like image1(please refer image 1)
But im getting image2(please refer image 2)
https://i.stack.imgur.com/nFTym.png //image 1
https://i.stack.imgur.com/MG99s.png //image 2

Answer 1

Assuming that the used data should appear in red, data should be defined as follows:
data: [used, total - used]
Please have a look at your amended code sample below.
const total = 300;
const used = 100;
var chart = new Chart(document.getElementById('myChart'), {
type: 'doughnut',
data: {
datasets: [{
label: 'My First dataset',
backgroundColor: ['red', 'green'],
borderColor: 'rgb(255, 99, 132)',
data: [used, total - used]
}]
},
options: {}
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.9.3/Chart.bundle.min.js"></script>
<canvas id="myChart" height="90"></canvas>