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):
<script src="RGraph.common.sheets.js"></script>
<script src="RGraph.common.key.js"></script>
<script src="RGraph.bar.js"></script>
<script>
new RGraph.Sheets('1ncvARBgXaDjzuca9i7Jyep6JTv9kms-bbIzyAxbaT0E', function (sheet)
{
var labels = sheet.get('A2:A7');
var key = sheet.get('B1:E1');
var data = [
sheet.get('B2:E2'),
sheet.get('B3:E3'),
sheet.get('B4:E4'),
sheet.get('B5:E5'),
sheet.get('B6:E6'),
sheet.get('B7:E7')
];
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>