reify/lib/fast-object.js

"use strict";

let fastProto = null;

// Creates an object with permanently fast properties in V8. See Toon Verwaest's
// post https://medium.com/@tverwaes/setting-up-prototypes-in-v8-ec9c9491dfe2#5f62
// for more details. Use %HasFastProperties(object) and the Node flag
// --allow-natives-syntax to check whether an object has fast properties.
function FastObject() {
  // A prototype object will have "fast properties" enabled once it is checked
  // against the inline property cache of a function, e.g. fastProto.property:
  // https://github.com/v8/v8/blob/6.0.122/test/mjsunit/fast-prototype.js#L48-L63
  if (fastProto !== null && typeof fastProto.property) {
    const result = fastProto;
    fastProto = FastObject.prototype = null;
    return result;
  }
  fastProto = FastObject.prototype = Object.create(null);
  return new FastObject;
}

// Initialize the inline property cache of FastObject.
FastObject();

module.exports = FastObject;