context.quadraticCurveTo(controlX, controlY, endingX, endingY)

Draws a quadratic curve starting at the current pen location to a given ending coordinate. Another given control coordinate determines the shape (curviness) of the curve.

https://s3-us-west-2.amazonaws.com/secure.notion-static.com/b489b51e-e188-4487-8d48-01d4e9c61283/Untitled.png

<!doctype html>
<html>
<head>
<style>
    body{ background-color:white; }
    #canvas{border:1px solid red; }
</style>
<script>
window.onload=(function(){

    // get a reference to the canvas element and it's context
    var canvas=document.getElementById("canvas");
    var ctx=canvas.getContext("2d");

    // arguments
    var startX=25;
    var startY=70;
    var controlX=75;
    var controlY=25;
    var endX=125;
    var endY=70;

    // A quadratic curve drawn using "moveTo" and "quadraticCurveTo" commands
    ctx.beginPath();
    ctx.moveTo(startX,startY);
    ctx.quadraticCurveTo(controlX,controlY,endX,endY);
    ctx.stroke();
}); // end window.onload
</script>
</head>
<body>
    <canvas id="canvas" width=200 height=150></canvas>
</body>
</html>