better

Rect.js

/**
 * Creates a new `Rect` with the specified top-left corner, width, and height.
 * These quantities can be specified in three different ways:
 *
 * - Four arguments, all `numbers`, specifying the x and y values of the
 *   top-left corner and width/height, respectively.
 * - Two arguments, both `V2`s.
 * - One argument, a single `Rect` to be cloned.
 *
 * @param {number | V2 | Rect} arg1
 * @param {number | V2 | void} arg2
 * @param {number | void} arg3
 * @param {number | void} arg4
 * @return {Rect}
 */
function Rect(arg1, arg2, arg3, arg4) {
    "use strict";
    if (typeof arg1 === "number") {
        this.x = arg1;
        this.y = arg2;
        this.width = arg3;
        this.height = arg4;
    } else if (arg1 instanceof V2) {
        this.x = arg1.x;
        this.y = arg1.y;
        this.width = arg2.x;
        this.height = arg2.y;
    } else {
        this.x = arg1.x;
        this.y = arg1.y;
        this.width = arg1.width;
        this.height = arg1.height;
    }
}

/**
 * Convenience function for `new Rect()`.
 *
 * @param {number | V2 | Rect} arg1
 * @param {number | V2 | void} arg2
 * @param {number | void} arg3
 * @param {number | void} arg4
 * @return {Rect}
 */
function rect(arg1, arg2, arg3, arg4) {
    "use strict";
    return new Rect(arg1, arg2, arg3, arg4);
}

/**
 * Decides if this rectangle contains the given point within it.
 *
 * The point can be specified as two separate `number`s or just a single `V2`.
 *
 * @param {number | V2} arg1
 * @param {number | void} arg2
 * @return {boolean}
 */
Rect.prototype.contains = function(arg1, arg2) {
    "use strict";
    if (typeof arg1 === "number") {
        return arg1 >= this.x &&
               arg2 >= this.y &&
               arg1 <= this.x + this.width &&
               arg2 <= this.y + this.height;
    }
    return arg1.x >= this.x &&
           arg1.y >= this.y &&
           arg1.x <= this.x + this.width &&
           arg1.y <= this.y + this.height;
};