ec39166 Feb 21, 2017
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@guybedford @unional @b-strauss @Rouche @cecchi
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SystemJS API

For setting SystemJS configuration see the Configuration API page.


Type: Function

SystemJS configuration helper function. See the Configuration API.


Type: Function

This represents the System base class, which can be extended or reinstantiated to create a custom System instance.


  var clonedSystemJS = new SystemJS.constructor();
  clonedSystemJS.import('x'); // imports in a custom context

SystemJS.getConfig() -> Object

Returns a clone of the internal SystemJS configuration in use.

SystemJS.delete(moduleName) -> Boolean

Type: Function

Deletes a module from the registry by normalized name. Returns true if the module was found in the registry before deletion.


Deprecated for System.registry.delete(moduleName)

SystemJS.get(moduleName) -> Module

Type: Function

Returns a module from the registry by normalized name.


Deprecated for System.registry.get(moduleName)

SystemJS.has(moduleName) -> Boolean

Type: Function

Returns whether a given module exists in the registry by normalized module name.

if (SystemJS.has('')) {
  // ...

Deprecated for System.registry.has(moduleName)

SystemJS.import(moduleName [, normalizedParentName]) -> Promise(Module)

Type: Function

Loads a module by name taking an optional normalized parent name argument.

Promise resolves to the ES module namespace value.

For loading relative to the current module, ES Modules define a __moduleName binding, so that:

SystemJS.import('./local', __moduleName);

In CommonJS modules the above would be instead.

This is non-standard, but covers a use case that will be provided by the spec.

SystemJS.isModule(Object) -> Boolean

Type: Function

Given any object, returns true if the object is either a SystemJS module or native JavaScript module object, and false otherwise. Useful for interop scenarios.

SystemJS.newModule(Object) -> Module

Type: Function

Given a plain JavaScript object, return an equivalent Module object.

Useful when writing a custom instantiate hook or using SystemJS.registry.set.

SystemJS.register([name ,] deps, declare)

Type: Function

Declaration function for defining modules of the System.register polyfill module format.

Read more on the format at the loader polyfill page

SystemJS.registerDynamic([name ,] deps, executingRequire, declare)

Type: Function

Companion module format to System.register for non-ES6 modules.

Provides a <script>-injection-compatible module format that any CommonJS or Global module can be converted into for CSP compatibility.

Output created by SystemJS Builder when creating bundles or self-executing bundles.

For example, the following CommonJS module:

module.exports = require('pkg/module');

Can be written:

System.registerDynamic(['pkg/module'], true, function(require, exports, module) {
  module.exports = require('pkg/module');
  • require is a standard CommonJS-style require
  • exports the CommonJS exports object, which is assigned to the default export of the module, with its own properties available as named exports.
  • module represents the CommonJS module object, with export and id properties set.


SystemJS registry object supporting:

  • SystemJS.registry.set(resolvedKey, namespace): Set a module namespace into the registry.
  • SystemJS.registry.get(resolvedKey): Get a module namespace (if any) from the registry.
  • SystemJS.registry.has(resolvedKey): Boolean indicating whether the given key is present in the registry.
  • `SystemJS.registry.delete(resolvedKey)``: Removes the given module from the registry (if any), returning true or false.
  • SystemJS.registry.keys: Function returning the keys iterator for the registry.
  • SystemJS.registry.values: Function returning the values iterator for the registry.
  • SystemJS.registry.entries: Function returning the entries iterator for the registry (keys and values).
  • SystemJS.registry[Symbol.iterator]: In supported environments, provides registry entries iteration.

See also SystemJS.newModule.

SystemJS.resolve(moduleName, [parentName]) -> Promise(string)

Type: Function

Resolves module name to normalized URL.

SystemJS.resolveSync(moduleName, [parentName]) -> string

Type: Function

Synchronous alternative to SystemJS.resolve.

SystemJS.set(moduleName, Module)

Type: Function

Sets a module into the registry directly and synchronously.

Typically used along with SystemJS.newModule to create a valid Module object:

SystemJS.set('custom-module', SystemJS.newModule({ prop: 'value' }));

Deprecated for System.registry.set(moduleName)

Note SystemJS stores all module names in the registry as normalized URLs. To be able to properly use the registry with SystemJS.set it is usually necessary to run SystemJS.set(SystemJS.resolveSync('custom-module'), SystemJS.newModule({ prop: 'value' })); to ensure that SystemJS.import behaves correctly.