Swizzle operator for the awesome https://github.com/toji/gl-matrix

gl-matrix.swizzle.js

var $each, $every, aliases;

$each = Function.prototype.call.bind(Array.prototype.forEach);
$every = Function.prototype.call.bind(Array.prototype.every);

aliases = {
  x: 'r', y: 'g', z: 'b', w: 'a'
};

function f(dest, channels, aliases) {
  $each(channels, (channel, index) => {
    dest[channel] = (vec) => vec[index];
    if (aliases) dest[aliases[channel]] = dest[channel];
  });

  return dest;
}

function proxify(target) {
  return new Proxy(target, {
    get: (target, channels) => {
      if (channels.length < 2 || channels.length > 4) {
        return target[channels];
      }

      if (channels in proxify.cache) {
        return proxify.cache[channels];
      }

      if (!$every(channels, (channel) => channel in target)) {
        return target[channels];
      }

      return (proxify.cache[channels] = function (vec) {
        var output, context;

        output = new vec.constructor(channels.length);
        context = this || target;

        $each(channels, (channel, index) => {
          output[index] = context[channel](vec);
        });

        return output;
      });
    }
  });
}

proxify.cache = {
  __proto__: null
};

vec2 = proxify(f(vec2, 'xy'));
vec3 = proxify(f(vec3, 'xyz', aliases));
vec4 = proxify(f(vec4, 'xyzw', aliases));