--- lang: en title: 'API docs: context.context' keywords: LoopBack 4.0, LoopBack 4, Node.js, TypeScript, OpenAPI sidebar: lb4_sidebar editurl: https://github.com/loopbackio/loopback-next/tree/master/packages/context permalink: /doc/en/lb4/apidocs.context.context.html --- [Home](./index.md) > [@loopback/context](./context.md) > [Context](./context.context.md) ## Context class Context provides an implementation of Inversion of Control (IoC) container **Signature:** ```typescript export declare class Context extends EventEmitter ``` **Extends:** EventEmitter ## Constructors
Constructor Modifiers Description
[(constructor)(\_parent, name)](./context.context._constructor_.md) Create a new context.
## Properties
Property Modifiers Type Description
[\_debug](./context.context._debug.md) `protected` Debugger A debug function which can be overridden by subclasses.
[\_parent?](./context.context._parent.md) `protected` [Context](./context.context.md) _(Optional)_ Parent context
[configResolver](./context.context.configresolver.md) `protected` [ConfigurationResolver](./context.configurationresolver.md) Configuration resolver
[name](./context.context.name.md) `readonly` string Name of the context
[registry](./context.context.registry.md) `protected` `readonly` Map<string, [Binding](./context.binding.md)> Key to binding map as the internal registry
[scope](./context.context.scope.md) [BindingScope](./context.bindingscope.md) Scope for binding resolution
[subscriptionManager](./context.context.subscriptionmanager.md) `readonly` [ContextSubscriptionManager](./context.contextsubscriptionmanager.md) Manager for observer subscriptions
[tagIndexer](./context.context.tagindexer.md) `protected` `readonly` ContextTagIndexer Indexer for bindings by tag
## Methods
Method Modifiers Description
[\_findByTagIndex(tag)](./context.context._findbytagindex.md) `protected` Find bindings by tag leveraging indexes
[\_mergeWithParent(childList, parentList)](./context.context._mergewithparent.md) `protected`
[add(binding)](./context.context.add.md) Add a binding to the context. If a locked binding already exists with the same key, an error will be thrown.
[bind(key)](./context.context.bind.md) Create a binding with the given key in the context. If a locked binding already exists with the same key, an error will be thrown.
[close()](./context.context.close.md) Close the context: clear observers, stop notifications, and remove event listeners from its parent context.
[configure(key)](./context.context.configure.md) Create a corresponding binding for configuration of the target bound by the given key in the context. For example, `ctx.configure('controllers.MyController').to({x: 1})` will create binding `controllers.MyController:$config` with value `{x: 1}`.
[contains(key)](./context.context.contains.md) Check if a binding exists with the given key in the local context without delegating to the parent context
[createView(filter, comparator, options)](./context.context.createview.md) Create a view of the context chain with the given binding filter
[debug(args)](./context.context.debug.md) `protected` Wrap the debug statement so that it always print out the context name as the prefix
[emitError(err)](./context.context.emiterror.md) Emit an `error` event
[emitEvent(type, event)](./context.context.emitevent.md) A strongly-typed method to emit context events
[find(pattern)](./context.context.find.md) Find bindings using a key pattern or filter function
[findByTag(tagFilter)](./context.context.findbytag.md) Find bindings using the tag filter. If the filter matches one of the binding tags, the binding is included.
[findOrCreateBinding(key, policy)](./context.context.findorcreatebinding.md) Find or create a binding for the given key
[get(keyWithPath, session)](./context.context.get.md) Get the value bound to the given key, throw an error when no value is bound for the given key.
[get(keyWithPath, options)](./context.context.get_1.md) Get the value bound to the given key, optionally return a (deep) property of the bound value.
[getBinding(key)](./context.context.getbinding.md) Look up a binding by key in the context and its ancestors. If no matching binding is found, an error will be thrown.
[getBinding(key, options)](./context.context.getbinding_1.md) Look up a binding by key in the context and its ancestors. If no matching binding is found and `options.optional` is not set to true, an error will be thrown.
[getConfig(key, propertyPath, resolutionOptions)](./context.context.getconfig.md) Resolve configuration for the binding by key
[getConfigAsValueOrPromise(key, propertyPath, resolutionOptions)](./context.context.getconfigasvalueorpromise.md) Get the value or promise of configuration for a given binding by key
[getConfigSync(key, propertyPath, resolutionOptions)](./context.context.getconfigsync.md) Resolve configuration synchronously for the binding by key
[getDebugNamespace()](./context.context.getdebugnamespace.md) `protected` Get the debug namespace for the context class. Subclasses can override this method to supply its own namespace.
[getOwnerContext(keyOrBinding)](./context.context.getownercontext.md) Get the owning context for a binding or its key
[getResolutionContext(binding)](./context.context.getresolutioncontext.md) Locate the resolution context for the given binding. Only bindings in the resolution context and its ancestors are visible as dependencies to resolve the given binding
[getScopedContext(scope)](./context.context.getscopedcontext.md) Get the context matching the scope
[getSync(keyWithPath, session)](./context.context.getsync.md) Get the synchronous value bound to the given key, optionally return a (deep) property of the bound value. This method throws an error if the bound value requires async computation (returns a promise). You should never rely on sync bindings in production code.
[getSync(keyWithPath, options)](./context.context.getsync_1.md) Get the synchronous value bound to the given key, optionally return a (deep) property of the bound value. This method throws an error if the bound value requires async computation (returns a promise). You should never rely on sync bindings in production code.
[inspect(options)](./context.context.inspect.md) Inspect the context and dump out a JSON object representing the context hierarchy
[isBound(key)](./context.context.isbound.md) Check if a key is bound in the context or its ancestors
[isSubscribed(observer)](./context.context.issubscribed.md) Check if an observer is subscribed to this context
[isVisibleTo(ctx)](./context.context.isvisibleto.md) Check if this context is visible (same or ancestor) to the given one
[on(eventName, listener)](./context.context.on.md) The "bind" event is emitted when a new binding is added to the context. The "unbind" event is emitted when an existing binding is removed.
[on(event, listener)](./context.context.on_1.md)
[once(eventName, listener)](./context.context.once.md) The "bind" event is emitted when a new binding is added to the context. The "unbind" event is emitted when an existing binding is removed.
[once(event, listener)](./context.context.once_1.md)
[setupConfigurationResolverIfNeeded()](./context.context.setupconfigurationresolverifneeded.md) `protected` Set up the configuration resolver if needed
[subscribe(observer)](./context.context.subscribe.md) Add a context event observer to the context
[toJSON()](./context.context.tojson.md) Create a plain JSON object for the context
[unbind(key)](./context.context.unbind.md) Unbind a binding from the context. No parent contexts will be checked.
[unsubscribe(observer)](./context.context.unsubscribe.md) Remove the context event observer from the context