systemjs/lib/proto.js

// SystemJS Loader Class and Extension helpers

function SystemJSLoader() {
  SystemLoader.call(this);

  systemJSConstructor.call(this);
}

// inline Object.create-style class extension
function SystemProto() {};
SystemProto.prototype = SystemLoader.prototype;
SystemJSLoader.prototype = new SystemProto();
SystemJSLoader.prototype.constructor = SystemJSLoader;

// remove ESML instantiate
SystemJSLoader.prototype.instantiate = function() {};

var systemJSConstructor;

function hook(name, hook) {
  SystemJSLoader.prototype[name] = hook(SystemJSLoader.prototype[name] || function() {});
}
function hookConstructor(hook) {
  systemJSConstructor = hook(systemJSConstructor || function() {});
}

function dedupe(deps) {
  var newDeps = [];
  for (var i = 0, l = deps.length; i < l; i++)
    if (indexOf.call(newDeps, deps[i]) == -1)
      newDeps.push(deps[i])
  return newDeps;
}

function group(deps) {
  var names = [];
  var indices = [];
  for (var i = 0, l = deps.length; i < l; i++) {
    var index = indexOf.call(names, deps[i]);
    if (index === -1) {
      names.push(deps[i]);
      indices.push([i]);
    }
    else {
      indices[index].push(i);
    }
  }
  return { names: names, indices: indices };
}

var getOwnPropertyDescriptor = true;
try {
  Object.getOwnPropertyDescriptor({ a: 0 }, 'a');
}
catch(e) {
  getOwnPropertyDescriptor = false;
}

// converts any module.exports object into an object ready for SystemJS.newModule
function getESModule(exports) {
  var esModule = {};
  // don't trigger getters/setters in environments that support them
  if (typeof exports == 'object' || typeof exports == 'function') {
    var hasOwnProperty = exports && exports.hasOwnProperty;
    if (getOwnPropertyDescriptor) {
      for (var p in exports) {
        if (!trySilentDefineProperty(esModule, exports, p))
          setPropertyIfHasOwnProperty(esModule, exports, p, hasOwnProperty);
      }
    }
    else {
      for (var p in exports)
        setPropertyIfHasOwnProperty(esModule, exports, p, hasOwnProperty);
    }
  }
  esModule['default'] = exports;
  defineProperty(esModule, '__useDefault', {
    value: true
  });
  return esModule;
}

function setPropertyIfHasOwnProperty(targetObj, sourceObj, propName, hasOwnProperty) {
  if (!hasOwnProperty || sourceObj.hasOwnProperty(propName))
    targetObj[propName] = sourceObj[propName];
}

function trySilentDefineProperty(targetObj, sourceObj, propName) {
  try {
    var d;
    if (d = Object.getOwnPropertyDescriptor(sourceObj, propName))
      defineProperty(targetObj, propName, d);

    return true;
  } catch (ex) {
    // Object.getOwnPropertyDescriptor threw an exception, fall back to normal set property.
    return false;
  }
}

function extend(a, b, prepend) {
  for (var p in b) {
    if (!prepend || !(p in a))
      a[p] = b[p];
  }
  return a;
}

// package configuration options
var packageProperties = ['main', 'format', 'defaultExtension', 'meta', 'map', 'basePath', 'depCache'];

// meta first-level extends where:
// array + array appends
// object + object extends
// other properties replace
function extendMeta(a, b, prepend) {
  for (var p in b) {
    var val = b[p];
    if (!(p in a))
      a[p] = val;
    else if (val instanceof Array && a[p] instanceof Array)
      a[p] = [].concat(prepend ? val : a[p]).concat(prepend ? a[p] : val);
    else if (typeof val == 'object' && val !== null && typeof a[p] == 'object')
      a[p] = extend(extend({}, a[p]), val, prepend);
    else if (!prepend)
      a[p] = val;
  }
}

function warn(msg) {
  if (this.warnings && typeof console != 'undefined' && console.warn)
    console.warn(msg);
}