Rotating 2D vector.

Vector2.js

/** Class representing a 2D vector. (X, Y)*/
export default class Vector2 {
    constructor(X = 0, Y = 0) {
        this.X = X
        this.Y = Y
    }
    /** Returns new Vector2 rotated by given angle (in radians) and any point.
     * @param {Number} rad Angle of rotation given in radians.
     * @param {Vector2} vector2 Point against which rotation is performed.
     * @returns {Vector2}
     */
    rotate(rad, vector2 = new Vector2(0, 0)) {
        const x = this.X - vector2.X
        const y = this.Y - vector2.Y

        return new Vector2(
            x * Math.cos(rad) - y * Math.sin(rad)
            + vector2.X,
            x * Math.sin(rad) + y * Math.cos(rad)
            + vector2.Y
        )
    }
}