JavaScript Bezier Function

// typeof but better
function getType(obj) {
    if (obj === null) return 'null';
    if (obj === undefined) return 'undefined';
    return obj.__proto__.constructor.name;
}

class Vector2 {
    constructor(x=0, y=0) {
        this.x = x;
        this.y = y;
    }

    lerp(t, v1, v2) {
        return new Vector2(lerp(t, a.x, b.x), lerp(t, a.y, b.y));
    }
}

// lerp functions
const lerp = (t, a, b) => t*(b-a)+a;
const slurp = (t, a, b) => new Vector2(lerp(t, a.x, b.x), lerp(t, a.y, b.y));

function bezier(t, ...pts) {
    let lerpFunc = lerp;
    if (getType(pts[0]) == 'Vector2') {
        lerpFunc = slurp;
    }

    if (pts.length == 2) {
        return lerpFunc(t, pts[0], pts[1]);
    }

    let bez1 = [...pts];
    let bez2 = [...pts];
    bez1.pop();
    bez2.shift();

    return lerpFunc(t, bezier(t, ...bez1), bezier(t, ...bez2));
}

console.log(bezier(0.5, 1, 0, 1, 0));