Es stands for which language

The acronyms began as telegraph codes. More Words At Play. Merriam-Webster's Words of the Week - Oct. Time Traveler. Love words? Need even more definitions? The Reference Record type is used to explain the behaviour of such operators as delete , typeof , the assignment operators, the super keyword and other language features.

For example, the left-hand operand of an assignment is expected to produce a Reference Record. A Reference Record is a resolved name or property binding; its fields are defined by Table The following abstract operations are used in this specification to operate upon Reference Records:.

The abstract operation GetValue takes argument V. The object that may be created in step 4. An implementation might choose to avoid the actual creation of the object. The abstract operation PutValue takes arguments V and W.

The object that may be created in step 5. An implementation might choose to avoid the actual creation of that object. The abstract operation GetThisValue takes argument V. The Property Descriptor type is used to explain the manipulation and reification of Object property attributes. Values of the Property Descriptor type are Records. Each field's name is an attribute name and its value is a corresponding attribute value as specified in 6.

In addition, any field may be present or absent. Property Descriptor values may be further classified as data Property Descriptors and accessor Property Descriptors based upon the existence or use of certain fields. A data Property Descriptor is one that includes any fields named either [[Value]] or [[Writable]]. An accessor Property Descriptor is one that includes any fields named either [[Get]] or [[Set]].

Any Property Descriptor may have fields named [[Enumerable]] and [[Configurable]]. A Property Descriptor value may not be both a data Property Descriptor and an accessor Property Descriptor; however, it may be neither. A fully populated Property Descriptor is one that is either an accessor Property Descriptor or a data Property Descriptor and that has all of the fields that correspond to the property attributes defined in either Table 3 or Table 4.

The following abstract operations are used in this specification to operate upon Property Descriptor values:. The abstract operation ToPropertyDescriptor takes argument Obj. The Environment Record type is used to explain the behaviour of name resolution in nested functions and blocks.

This type and the operations upon it are defined in 9. The Abstract Closure specification type is used to refer to algorithm steps together with a collection of values.

Abstract Closures are meta-values and are invoked using function application style such as closure arg1 , arg2. Like abstract operations , invocations perform the algorithm steps described by the Abstract Closure. In algorithm steps that create an Abstract Closure, values are captured with the verb "capture" followed by a list of aliases.

When an Abstract Closure is created, it captures the value that is associated with each alias at that time. In steps that specify the algorithm to be performed when an Abstract Closure is called, each captured value is referred to by the alias that was used to capture the value. Abstract Closures are created inline as part of other algorithms, shown in the following example. The Data Block specification type is used to describe a distinct and mutable sequence of byte-sized 8 bit numeric values.

A byte value is an integer value in the range 0 through , inclusive. A Data Block value is created with a fixed number of bytes that each have the initial value 0. For notational convenience within this specification, an array-like syntax can be used to access the individual bytes of a Data Block value. This notation presents a Data Block value as a 0-origined integer -indexed sequence of bytes. For example, if db is a 5 byte Data Block value then db [2] can be used to access its 3 rd byte.

A data block that resides in memory that can be referenced from multiple agents concurrently is designated a Shared Data Block. A Shared Data Block has an identity for the purposes of equality testing Shared Data Block values that is address-free : it is tied not to the virtual addresses the block is mapped to in any process, but to the set of locations in memory that the block represents.

Two data blocks are equal only if the sets of the locations they contain are equal; otherwise, they are not equal and the intersection of the sets of locations they contain is empty. Abstract operations below introduce Shared Data Block events and act as the interface between evaluation semantics and the event semantics of the memory model.

The events form a candidate execution , on which the memory model acts as a filter. Please consult the memory model for full semantics. Shared Data Block events are modeled by Records , defined in the memory model.

The following abstract operations are used in this specification to operate upon Data Block values:. The abstract operation CreateByteDataBlock takes argument size a non-negative integer. The PrivateElement type is a Record used in the specification of private class fields, methods, and accessors. Although Property Descriptors are not used for private elements, private fields behave similarly to non-configurable, non-enumerable, writable data properties , private methods behave similarly to non-configurable, non-enumerable, non-writable data properties , and private accessors behave similarly to non-configurable, non-enumerable accessor properties.

Values of the PrivateElement type are Record values whose fields are defined by Table Such values are referred to as PrivateElements. The ClassFieldDefinition type is a Record used in the specification of class fields. Such values are referred to as ClassFieldDefinition Records. The Private Name specification type is used to describe a globally unique value one which differs from any other Private Name, even if they are otherwise indistinguishable which represents the key of a private class element field, method, or accessor.

Each Private Name has an associated immutable [[Description]] which is a String value. A ClassStaticBlockDefinition Record is a Record value used to encapsulate the executable code for a class static initialization block. Other, more specialized abstract operations are defined throughout this specification.

To clarify the semantics of certain constructs it is useful to define a set of conversion abstract operations. The conversion abstract operations are polymorphic; they can accept a value of any ECMAScript language type. But no other specification types are used with these operations.

It converts its input argument to a non-Object type. If an object is capable of converting to more than one primitive type, it may use the optional hint preferredType to favour that type. When ToPrimitive is called without a hint, then it generally behaves as if the hint were number. However, objects may over-ride this behaviour by defining a toPrimitive method. Of the objects defined in this specification only Dates see Dates treat the absence of a hint as if the hint were string. The abstract operation ToBoolean takes argument argument.

It converts argument to a value of type Boolean according to Table 14 :. The abstract operation ToNumeric takes argument value. It returns value converted to a Number or a BigInt. The abstract operation ToNumber takes argument argument. It converts argument to a value of type Number according to Table 15 :.

The abstract operation StringToNumber specifies how to convert a String value to a Number value , using the following grammar. All grammar symbols not explicitly defined above have the definitions used in the Lexical Grammar for numeric literals Some differences should be noted between the syntax of a StringNumericLiteral and a NumericLiteral :. The abstract operation StringToNumber takes argument str a String. It returns a Number. The abstract operation RoundMVResult takes argument n a mathematical value.

It converts n to a Number in an implementation-defined manner. For the purposes of this abstract operation, a digit is significant if it is not zero or there is a non-zero digit to its left and there is a non-zero digit to its right.

For the purposes of this abstract operation, "the mathematical value denoted by" a representation of a mathematical value is the inverse of "the decimal representation of" a mathematical value.

The abstract operation ToInt32 takes argument argument. The abstract operation ToUint32 takes argument argument. The abstract operation ToInt16 takes argument argument. The abstract operation ToUint16 takes argument argument. The abstract operation ToInt8 takes argument argument. The abstract operation ToUint8 takes argument argument. The abstract operation ToUint8Clamp takes argument argument.

This differs from Math. The abstract operation ToBigInt takes argument argument. It converts argument to a BigInt value, or throws if an implicit conversion from Number would be required. It returns a BigInt or undefined. StringToBigInt uses the following grammar. The abstract operation ToBigInt64 takes argument argument. The abstract operation ToBigUint64 takes argument argument. The abstract operation ToString takes argument argument. It converts argument to a value of type String according to Table 17 :.

The abstract operation ToObject takes argument argument. It converts argument to a value of type Object according to Table 18 :. The abstract operation ToPropertyKey takes argument argument. It converts argument to a value that can be used as a property key. It clamps argument to an integral Number suitable for use as the length of an array-like object. It returns argument converted to a Number value if it is a String representation of a Number that would be produced by ToString , or the string "-0".

Otherwise, it returns undefined. A canonical numeric string is any String value for which the CanonicalNumericIndexString abstract operation does not return undefined. It converts value to a non-negative integer if the corresponding decimal representation, as a String, is an integer index.

The abstract operation RequireObjectCoercible takes argument argument. It throws an error if argument is a value that cannot be converted to an Object using ToObject. It is defined by Table 19 :.

The abstract operation IsArray takes argument argument. It determines if argument is a callable function with a [[Call]] internal method. It determines if argument is a function object with a [[Construct]] internal method. The abstract operation IsExtensible takes argument O an Object. It returns a completion record which, if its [[Type]] is normal , has a [[Value]] which is a Boolean.

It is used to determine whether additional properties can be added to O. The abstract operation IsIntegralNumber takes argument argument. It determines if argument is a finite integral Number value. It determines if argument is a value that may be used as a property key. The abstract operation IsRegExp takes argument argument. It determines if p is a prefix of q. It interprets string as a sequence of UTF encoded code points, as described in 6.

It returns a completion record whose [[Type]] is normal and whose [[Value]] is a Boolean indicating whether or not the two arguments are the same value. It returns a completion record whose [[Type]] is normal and whose [[Value]] is a Boolean. The LeftFirst flag is used to control the order in which operations with potentially visible side-effects are performed upon x and y.

If LeftFirst is true , the x parameter corresponds to an expression that occurs to the left of the y parameter's corresponding expression. If LeftFirst is false , the reverse is the case and operations must be performed upon y before x.

Step 3 differs from step 2. The comparison of Strings uses a simple lexicographic ordering on sequences of code unit values. There is no attempt to use the more complex, semantically oriented definitions of character or string equality and collating order defined in the Unicode specification. Therefore String values that are canonically equal according to the Unicode standard could test as unequal. In effect this algorithm assumes that both Strings are already in normalized form.

Also, note that for strings containing supplementary characters, lexicographic ordering on sequences of UTF code unit values differs from that on sequences of code point values. It is the source of all ECMAScript objects that are created algorithmically, including both ordinary objects and exotic objects.

It factors out common steps used in creating all objects, and centralizes object creation. Within this specification, exotic objects are created in abstract operations such as ArrayCreate and BoundFunctionCreate by first calling MakeBasicObject to obtain a basic, foundational object, and then overriding some or all of that object's internal methods.

In order to encapsulate exotic object creation, the object's essential internal methods are never modified outside those operations. The abstract operation Get takes arguments O an Object and P a property key.

It is used to retrieve the value of a specific property of an object. If the value is not an object, the property lookup is performed using a wrapper object appropriate for the type of the value.

It is used to set the value of a specific property of an object. V is the new value for the property. It is used to create a new own property of an object. This abstract operation creates a property whose attributes are set to the same defaults used for properties created by the ECMAScript language assignment operator. Normally, the property will not already exist. If it does exist and is not configurable or if O is not extensible, [[DefineOwnProperty]] will return false.

This abstract operation creates a property whose attributes are set to the same defaults used for built-in methods and methods defined using class declaration syntax. It throws a TypeError exception if the requested property update cannot be performed. If it does exist and is not configurable or if O is not extensible, [[DefineOwnProperty]] will return false causing this operation to throw a TypeError exception. It is used to create a new non-enumerable own property of an object. This abstract operation creates a property whose attributes are set to the same defaults used for properties created by the ECMAScript language assignment operator except it is not enumerable.

It is used to call the [[DefineOwnProperty]] internal method of an object in a manner that will throw a TypeError exception if the requested property update cannot be performed.

It is used to remove a specific own property of an object. It throws an exception if the property is not configurable. It is used to get the value of a specific property of an ECMAScript language value when the value of the property is expected to be a function. It is used to determine whether an object has a property with the specified property key. The property may be either an own or inherited. It is used to determine whether an object has an own property with the specified property key.

It is used to call the [[Call]] internal method of a function object. F is the function object , V is an ECMAScript language value that is the this value of the [[Call]], and argumentsList is the value passed to the corresponding argument of the internal method. If argumentsList is not present, a new empty List is used as its value.

The abstract operation Construct takes argument F a constructor and optional arguments argumentsList and newTarget a constructor. It is used to call the [[Construct]] internal method of a function object. If newTarget is not present, F is used as its value. If newTarget is not present, this operation is equivalent to: new F It is used to fix the set of own properties of an object. It is used to determine if the set of own properties of an object are fixed. It is used to create an Array whose elements are provided by elements.

It returns the value of the "length" property of an array-like object as a non-negative integer. An array-like object is any object for which this operation returns an integer rather than an abrupt completion. It is used to create a List value whose elements are provided by the indexed properties of obj. V serves as both the lookup point for the property and the this value of the call.

It implements the default algorithm for determining if O inherits from the instance object inheritance path provided by C. The abstract operation SpeciesConstructor takes arguments O an Object and defaultConstructor a constructor. It is used to retrieve the constructor that should be used to create new objects that are derived from O.

The abstract operation GetFunctionRealm takes argument obj a function object. Step 4 will only be reached if obj is a non-standard function exotic object that does not have a [[Realm]] internal slot. The target passed in here is always a newly created object which is not directly accessible in case of an error being thrown. See Common Iteration Interfaces The abstract operation GetIterator takes argument obj and optional arguments hint sync or async and method.

The abstract operation IteratorNext takes argument iteratorRecord and optional argument value. The abstract operation IteratorComplete takes argument iterResult an Object. The abstract operation IteratorValue takes argument iterResult an Object. The abstract operation IteratorStep takes argument iteratorRecord.

It requests the next value from iteratorRecord. The abstract operation IteratorClose takes arguments iteratorRecord and completion a Completion Record. It is used to notify an iterator that it should perform any actions it would normally perform when it has reached its completed state. An algorithm step of the form:. It is used to notify an async iterator that it should perform any actions it would normally perform when it has reached its completed state.

It creates an object that conforms to the IteratorResult interface. The abstract operation CreateListIteratorRecord takes argument list. It creates an Iterator The abstract operation IterableToList takes argument items and optional argument method.

In addition to those defined in this section, specialized syntax-directed operations are defined throughout this specification. This is done only for ease of specification, so that anonymous default exports can be resolved like any other export. NaN LN10 LN2 LOG10E LOG2E PI SQRT2 Normative Optional. Normative Optional , Legacy. There are only two Boolean values, true and false.

Parse Nodes are specification artefacts, and implementations are not required to use an analogous data structure.

Finite-precision multiplication is commutative, but not always associative. Finite-precision addition is commutative, but not always associative. The least significant digit of s is not always uniquely determined by the requirements listed in step 5. If there are two such possible values of s , choose the one that is even.

Note that k is the number of digits in the decimal representation of s and that s is not divisible by Gay for binary-to-decimal conversion of floating-point numbers: Gay, David M. Even if the result has a much larger bit width than the input, the exact mathematical answer is given. Semantics here should be equivalent to a bitwise shift, treating the BigInt as an infinite length string of binary two's complement digits.

The two properties above are called irreflexivity and transitivity, respectively. The three properties above are called totality, irreflexivity, and transitivity, respectively. Await can be combined with the? Await value. ReturnIfAbrupt result. A StringNumericLiteral that is decimal may have any number of leading 0 digits.

Given the above definition of ToInt The ToInt32 abstract operation is idempotent: if applied to a result that it produced, the second application leaves that value unchanged. The ToUint32 abstract operation is idempotent: if applied to a result that it produced, the second application leaves that value unchanged.

Given the above definition of ToUint The substitution of 2 16 for 2 32 in step 4 is the only difference between ToUint32 and ToUint Typically, an array-like object would also have some properties with integer index names.

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