vec.js

const vec2 = (() => {
    function add(other)  { return vec2(this.x + other.x, this.y + other.y) }
    function sub(other)  { return vec2(this.x - other.x, this.y - other.y) }
    function mul(val)    { return vec2(this.x * val, this.y * val) }
    function div(val)    { return vec2(this.x / val, this.y / val) }
    function length()    { return Math.hypot(this.x, this.y) }
    function angle()     { return Math.atan2(this.y, this.x) }
    function turn(a)     { return vec2(
        this.x*Math.cos(a) - this.y*Math.sin(a),
        this.x*Math.sin(a) + this.y*Math.cos(a)
    ) }
    function dot(other)  { return this.x*other.x + this.y*other.y }
    function normalize() {
        const len = this.length();
        return vec2(this.x / len, this.y / len);
    }
    function map(fn) { return vec2(fn(this.x, 'x'), fn(this.y, 'y')); }
    return (x, y) => ({
        x, y,
        0: x, 1: y,
        *[Symbol.iterator]() { yield* [x, y]; },
        add, sub,
        mul, div,
        length, normalize,
        angle, turn,
        dot,
        map,
        xy: { x, y },
    })
})();

const vec3 = (() => {
    function add(other) { return vec3(this.x + other.x, this.y + other.y, this.z + other.z) }
    function sub(other) { return vec3(this.x - other.x, this.y - other.y, this.z - other.z) }
    function mul(val)   { return vec3(this.x * val, this.y * val, this.z * val) }
    function div(val)   { return vec3(this.x / val, this.y / val, this.z / val) }
    function length()   { return Math.hypot(this.x, this.y, this.z) }
    function dot(other) { return this.x * other.x + this.y * other.y + this.z * other.z }
    function cross(other) {
        return vec3(
            this.y * other.z - this.z * other.y,
            this.z * other.x - this.x * other.z,
            this.x * other.y - this.y * other.x
        )
    }
    function normalize() {
        const len = this.length();
        return vec3(this.x / len, this.y / len, this.z / len);
    }
    function map(fn) { return vec2(fn(this.x, 'x'), fn(this.y, 'y')); }
    return (x, y, z) => ({
        x, y, z,
        add, sub,
        mul, div,
        length,
        dot, cross,
        normalize,
        map,
        xyz: { x, y, z },
    })
})();