Draws a rectangle with rounded corners on a canvas.

drawRoundedRect.js

function drawRoundedRect(context, x, y, width, height, borderRadius) {
    if (!borderRadius) {
        context.rect(x, y, width, height);
    } else {
        var widthMinusRad = width - borderRadius;
        var heightMinusRad = height - borderRadius;
        context.translate(x, y);
        context.arc(borderRadius, borderRadius, borderRadius, Math.PI, Math.PI * 1.5);
        context.lineTo(widthMinusRad, 0);
        context.arc(widthMinusRad, borderRadius, borderRadius, Math.PI * 1.5, Math.PI * 2);
        context.lineTo(width, heightMinusRad);
        context.arc(widthMinusRad, heightMinusRad, borderRadius, Math.PI * 2, Math.PI * 0.5);
        context.lineTo(borderRadius, height);
        context.arc(borderRadius, heightMinusRad, borderRadius, Math.PI * 0.5, Math.PI);
        context.translate(-x, -y);
    }
};