ECMA-262 (12th Edition) ECMAScript 2021 Language Specification - page 1

the same specifications for all of those methods except for GetBindingValue, DeleteBinding, HasThisBinding and
GetThisBinding. In addition, module Environment Records support the methods listed in

Table 22

Global function declarations are always represented as own properties of the

global object

. If

possible, an existing own property is reconfigured to have a standard set of attribute values. Step

is equivalent to what calling the InitializeBinding concrete method would do and if

globalObject

is a Proxy will produce the same sequence of Proxy trap calls.

9.1.1.4.18 CreateGlobalFunctionBinding (

)

9.1.1.5 Module Environment Records

202

Table 22: Additional Methods of Module Environment Records

Method

Purpose

CreateImportBinding(N,
M, N2)

Create an immutable indirect binding in a

module Environment Record

. The String value

is the text of the bound name.

is a

Module Record

, and

is a binding that exists in

module Environment Record

GetThisBinding()

Return the value of this

Environment Record

this

binding.

The behaviour of the additional concrete specification methods for module Environment Records are defined by the
following algorithms:

The GetBindingValue concrete method of a

module Environment Record

envRec

takes arguments

(a String) and

Boolean). It returns the value of its bound identifier whose name is the value of the argument

. However, if the

binding is an indirect binding the value of the target binding is returned. If the binding exists but is uninitialized a

ReferenceError

is thrown. It performs the following steps when called:

Assert

true

Assert

envRec

has a binding for

3. If the binding for

is an indirect binding, then

a. Let

and

be the indirection values provided when this binding for

was created.

b. Let

targetEnv

.[[Environment]].

c. If

targetEnv

undefined

, throw a

ReferenceError

exception.

d. Return ?

targetEnv

.GetBindingValue(

true

4. If the binding for

envRec

is an uninitialized binding, throw a

ReferenceError

exception.

5. Return the value currently bound to

envRec

NOTE

The DeleteBinding concrete method of a

module Environment Record

is never used within this specification.

NOTE

The HasThisBinding concrete method of a

module Environment Record

envRec

takes no arguments. It performs the

following steps when called:

1. Return

true

will always be

true

because a

Module

is always

strict mode code

Module Environment Records are only used within strict code and an

early error

rule prevents

the delete operator, in strict code, from being applied to a

Reference Record

that would resolve to

module Environment Record

binding. See

13.5.1.1

9.1.1.5.1 GetBindingValue (

)

9.1.1.5.2 DeleteBinding (

)

9.1.1.5.3 HasThisBinding ( )

203

NOTE

The GetThisBinding concrete method of a

module Environment Record

envRec

takes no arguments. It performs the

following steps when called:

1. Return

undefined

The CreateImportBinding concrete method of a

module Environment Record

envRec

takes arguments

(a String),

Module Record

), and

(a String). It creates a new initialized immutable indirect binding for the name

. A

binding must not already exist in this

Environment Record

for

is the name of a binding that exists in

module Environment Record

. Accesses to the value of the new binding will indirectly access the bound value of the

target binding. It performs the following steps when called:

Assert

envRec

does not already have a binding for

: When

.[[Environment]] is instantiated it will have a direct binding for

4. Create an immutable indirect binding in

envRec

for

that references

and

as its target binding and record

that the binding is initialized.

5. Return

NormalCompletion

(

empty

The following

abstract operations

are used in this specification to operate upon Environment Records:

The abstract operation GetIdentifierReference takes arguments

env

(an

Environment Record

null

name

(a String),

and

strict

(a Boolean). It performs the following steps when called:

1. If

env

is the value

null

, then

a. Return the

Reference Record

{ [[Base]]:

unresolvable

, [[ReferencedName]]:

name

, [[Strict]]:

strict

[[ThisValue]]:

empty

2. Let

exists

be ?

env

.HasBinding(

name

3. If

exists

true

, then

a. Return the

Reference Record

{ [[Base]]:

env

, [[ReferencedName]]:

name

, [[Strict]]:

strict

, [[ThisValue]]:

empty

4. Else,

a. Let

outer

env

.[[OuterEnv]].

b. Return ?

GetIdentifierReference

(

outer

name

strict

The abstract operation NewDeclarativeEnvironment takes argument

(an

Environment Record

). It performs the

following steps when called:

Module Environment Records always provide a

this

binding.

9.1.1.5.4 GetThisBinding ( )

9.1.1.5.5 CreateImportBinding (

)

9.1.2 Environment Record Operations

9.1.2.1 GetIdentifierReference (

env

name

strict

)

9.1.2.2 NewDeclarativeEnvironment (

)

204

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