You can read Google Sheets spreadsheets data in JavaScript by using the RGraph sheets connector:
https://www.rgraph.net/canvas/docs/import-data-from-google-sheets.html
Initially (a few years ago) this relied on some RGraph functions to work its magic - but now it can work standalone (ie not requiring the RGraph common library).
Some example code (this example makes an RGraph chart):
<!-- Include the sheets library -->
<script src="RGraph.common.sheets.js"></script>
<!-- Include these two RGraph libraries to make the chart -->
<script src="RGraph.common.key.js"></script>
<script src="RGraph.bar.js"></script>
<script>
// Create a new RGraph Sheets object using the spreadsheet's key and
// the callback function that creates the chart. The RGraph.Sheets object is
// passed to the callback function as an argument so it doesn't need to be
// assigned to a variable when it's created
new RGraph.Sheets('1ncvARBgXaDjzuca9i7Jyep6JTv9kms-bbIzyAxbaT0E', function (sheet)
{
// Get the labels from the spreadsheet by retrieving part of the first row
var labels = sheet.get('A2:A7');
// Use the column headers (ie the names) as the key
var key = sheet.get('B1:E1');
// Get the data from the sheet as the data for the chart
var data = [
sheet.get('B2:E2'), // January
sheet.get('B3:E3'), // February
sheet.get('B4:E4'), // March
sheet.get('B5:E5'), // April
sheet.get('B6:E6'), // May
sheet.get('B7:E7') // June
];
// Create and configure the chart; using the information retrieved above
// from the spreadsheet
var bar = new RGraph.Bar({
id: 'cvs',
data: data,
options: {
backgroundGridVlines: false,
backgroundGridBorder: false,
xaxisLabels: labels,
xaxisLabelsOffsety: 5,
colors: ['#A8E6CF','#DCEDC1','#FFD3B6','#FFAAA5'],
shadow: false,
colorsStroke: 'rgba(0,0,0,0)',
yaxis: false,
marginLeft: 40,
marginBottom: 35,
marginRight: 40,
key: key,
keyBoxed: false,
keyPosition: 'margin',
keyTextSize: 12,
textSize: 12,
textAccessible: false,
axesColor: '#aaa'
}
}).wave();
});
</script>