Find the corner position of a rotade rectangle in javascript

calculateRotatedPositions.js

// rotation variable is the rotation of the rect in radians
// rectWidth is the width of the rectangle in question
// rectX is the x position of the top left most corner of the rectangle
// rectY is the y position of the top left most corner of the rectangle

const rotatedXDelta = rectWidth * Math.cos(rotation);
const rotatedYDelta = rectWidth * Math.sin(rotation);

const rotatedX = rectX + rotatedXDelta;
const rotatedY = rectY + rotatedYDelta;

// Based on a top left most rotational origo this will give the position of the top right most corner of the rectangle