aurelia-polyfills/src/reflect.js

The minimal set of polyfills that the Aurelia platform needs to run on ES5 browsers.

import {PLATFORM} from 'aurelia-pal';

if (typeof FEATURE_NO_ES2015 === 'undefined') {

const bind = Function.prototype.bind;

if (typeof PLATFORM.global.Reflect === 'undefined') {
  PLATFORM.global.Reflect = {};
}

if (typeof Reflect.defineProperty !== 'function') {
  Reflect.defineProperty = function(target, propertyKey, descriptor) {
    if (typeof target === 'object' ? target === null : typeof target !== 'function') {
      throw new TypeError('Reflect.defineProperty called on non-object');
    }
    try {
      Object.defineProperty(target, propertyKey, descriptor);
      return true;
    } catch (e) {
      return false;
    }
  };
}

if (typeof Reflect.construct !== 'function') {
  Reflect.construct = function(Target, args) {
    if (args) {
      switch (args.length){
        case 0: return new Target();
        case 1: return new Target(args[0]);
        case 2: return new Target(args[0], args[1]);
        case 3: return new Target(args[0], args[1], args[2]);
        case 4: return new Target(args[0], args[1], args[2], args[3]);
      }
    }

    var a = [null];
    a.push.apply(a, args);
    return new (bind.apply(Target, a));
  };
}

if (typeof Reflect.ownKeys !== 'function') {
  Reflect.ownKeys = function(o) { return (Object.getOwnPropertyNames(o).concat(Object.getOwnPropertySymbols(o))); }
}

} // endif FEATURE_NO_ES2015

if (typeof FEATURE_NO_ESNEXT === 'undefined') {

const emptyMetadata = Object.freeze({});
const metadataContainerKey = '__metadata__';

if (typeof Reflect.getOwnMetadata !== 'function') {
  Reflect.getOwnMetadata = function(metadataKey, target, targetKey) {
    if (target.hasOwnProperty(metadataContainerKey)) {
      return (target[metadataContainerKey][targetKey] || emptyMetadata)[metadataKey];
    }
  };
}

if (typeof Reflect.defineMetadata !== 'function') {
  Reflect.defineMetadata = function(metadataKey, metadataValue, target, targetKey) {
    let metadataContainer = target.hasOwnProperty(metadataContainerKey) ? target[metadataContainerKey] : (target[metadataContainerKey] = {});
    let targetContainer = metadataContainer[targetKey] || (metadataContainer[targetKey] = {});
    targetContainer[metadataKey] = metadataValue;
  };
}

if (typeof Reflect.metadata !== 'function') {
  Reflect.metadata = function(metadataKey, metadataValue) {
    return function(target, targetKey) {
      Reflect.defineMetadata(metadataKey, metadataValue, target, targetKey);
    };
  };
}

} // endif FEATURE_NO_ESNEXT