---
lang: en
title: 'API docs: context.binding'
keywords: LoopBack 4.0, LoopBack 4, Node.js, TypeScript, OpenAPI
sidebar: lb4_sidebar
editurl: https://github.com/strongloop/loopback-next/tree/master/packages/context
permalink: /doc/en/lb4/apidocs.context.binding.html
---
[Home](./index.md) > [@loopback/context](./context.md) > [Binding](./context.binding.md)
## Binding class
Binding represents an entry in the `Context`. Each binding has a key and a corresponding value getter.
Signature:
```typescript
export declare class Binding extends EventEmitter
```
Extends: EventEmitter
## Constructors
| Constructor | Modifiers | Description |
| --- | --- | --- |
| [(constructor)(key, isLocked)](./context.binding._constructor_.md) | | Constructs a new instance of the Binding class |
## Properties
| Property | Modifiers | Type | Description |
| --- | --- | --- | --- |
| [isLocked](./context.binding.islocked.md) | | boolean | |
| [key](./context.binding.key.md) | | string | Key of the binding |
| [providerConstructor](./context.binding.providerconstructor.md) | | [Constructor](./context.constructor.md)<[Provider](./context.provider.md)<T>> \| undefined | For bindings bound via toProvider(), this property contains the constructor function of the provider class |
| [scope](./context.binding.scope.md) | | [BindingScope](./context.bindingscope.md) | Scope of the binding to control how the value is cached/shared |
| [source](./context.binding.source.md) | | [BindingSource](./context.bindingsource.md)<T> \| undefined | |
| [tagMap](./context.binding.tagmap.md) | | [TagMap](./context.tagmap.md) | Map for tag name/value pairs |
| [tagNames](./context.binding.tagnames.md) | | string\[\] | Get an array of tag names |
| [type](./context.binding.type.md) | | [BindingType](./context.bindingtype.md) \| undefined | Type of the binding value getter |
| [valueConstructor](./context.binding.valueconstructor.md) | | [Constructor](./context.constructor.md)<T> \| undefined | For bindings bound via toClass(), this property contains the constructor function of the class |
## Methods
| Method | Modifiers | Description |
| --- | --- | --- |
| [apply(templateFns)](./context.binding.apply.md) | | Apply one or more template functions to set up the binding with scope, tags, and other attributes as a group. |
| [applyDefaultScope(scope)](./context.binding.applydefaultscope.md) | | Apply default scope to the binding. It only changes the scope if it's not set yet |
| [bind(key)](./context.binding.bind.md) | static | A static method to create a binding so that we can do Binding.bind('foo').to('bar'); as new Binding('foo').to('bar') is not easy to read. |
| [configure(key)](./context.binding.configure.md) | static | Create a configuration binding for the given key |
| [getValue(ctx, session)](./context.binding.getvalue.md) | | This is an internal function optimized for performance. Users should use @inject(key) or ctx.get(key) instead.Get the value bound to this key. Depending on isSync, this function returns either: - the bound value - a promise of the bound valueConsumers wishing to consume sync values directly should use isPromiseLike to check the type of the returned value to decide how to handle it. |
| [getValue(ctx, options)](./context.binding.getvalue_1.md) | | Returns a value or promise for this binding in the given context. The resolved value can be undefined if optional is set to true in options. |
| [inScope(scope)](./context.binding.inscope.md) | | Set the binding scope |
| [inspect(options)](./context.binding.inspect.md) | | Inspect the binding to return a json representation of the binding information |
| [lock()](./context.binding.lock.md) | | Lock the binding so that it cannot be rebound |
| [on(eventName, listener)](./context.binding.on.md) | | The "changed" event is emitted by methods such as tag, inScope, to, and toClass. |
| [on(event, listener)](./context.binding.on_1.md) | | |
| [once(eventName, listener)](./context.binding.once.md) | | The "changed" event is emitted by methods such as tag, inScope, to, and toClass. |
| [once(event, listener)](./context.binding.once_1.md) | | |
| [refresh(ctx)](./context.binding.refresh.md) | | Invalidate the binding cache so that its value will be reloaded next time. This is useful to force reloading a cached value when its configuration or dependencies are changed. \*\*WARNING\*\*: The state held in the cached value will be gone. |
| [tag(tags)](./context.binding.tag.md) | | Tag the binding with names or name/value objects. A tag has a name and an optional value. If not supplied, the tag name is used as the value. |
| [to(value)](./context.binding.to.md) | | Bind the key to a constant value. The value must be already available at binding time, it is not allowed to pass a Promise instance. |
| [toAlias(keyWithPath)](./context.binding.toalias.md) | | Bind the key to an alias of another binding |
| [toClass(ctor)](./context.binding.toclass.md) | | Bind the key to an instance of the given class. |
| [toDynamicValue(factory)](./context.binding.todynamicvalue.md) | | Bind the key to a computed (dynamic) value. |
| [toInjectable(ctor)](./context.binding.toinjectable.md) | | Bind to a class optionally decorated with @injectable. Based on the introspection of the class, it calls toClass/toProvider/toDynamicValue internally. The current binding key will be preserved (not being overridden by the key inferred from the class or options).This is similar to [createBindingFromClass()](./context.createbindingfromclass.md) but applies to an existing binding. |
| [toJSON()](./context.binding.tojson.md) | | Convert to a plain JSON object |
| [toProvider(providerClass)](./context.binding.toprovider.md) | | Bind the key to a value computed by a Provider.\* |
| [unlock()](./context.binding.unlock.md) | | Unlock the binding |