npm i @balkangraph/flowchart.js

<script src="https://balkan.app/js/flowchart.js"></script>
<style>
    html, body, #chart{
        width: 100%;
        height: 100%;
        margin: 0;
    }
</style>
<div id="chart"></div>
<script>
let chart = new FlowChart('#chart');
chart.onChanged(function(){
    var data = chart.json();
    //post data to server
});
chart.load({
        nodes: [
            { id: 1, templateId: 'process', x: 400, y: 150, fill: "#FFCA28" },
            { id: 2, templateId: 'decision', x: 400, y: 350, fill: "#F57C00" },
            { id: 3, templateId: 'process', x: 700, y: 350 }
        ],
        links: [
            { from: 1, to: 2 },
            { from: 2, to: 3 }
        ]
    }
); 
</script>