js

package
v1.15.0 Latest Latest
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 Go to latest Published: Nov 12, 2026 License: MIT Imports: 27 Imported by: 0

Documentation

Overview

Package js is a Go model of JavaScript values with the language's exact semantics, for components that tern build compiles to Go (ADR 0011). Generated code calls it; it is not covered by the stability promise.

A Value is one of: 

Undefined, Null       the two sentinels
bool                  a boolean
float64               a number
string                a string, UTF-8 encoded; lengths and indexes are UTF-16
*Object               an object, including functions and arrays
*Symbol               a symbol

Index

Constants

View Source 
const (
	CtlNone = iota
	CtlReturn
	CtlBreak
	CtlContinue
)

Control codes: how a try block's closure was left.

View Source 
const MaxDepth = 10000

MaxDepth is how deep calls may nest before a RangeError, as engines have: Go's stack would otherwise overflow, which ends the process.

Variables

View Source 
var (
	SymbolIterator    = &Symbol{"Symbol.iterator"}
	SymbolToPrimitive = &Symbol{"Symbol.toPrimitive"}
	// SymbolAsyncIterator is Symbol.asyncIterator.
	SymbolAsyncIterator = &Symbol{"Symbol.asyncIterator"}
	SymbolToStringTag   = &Symbol{"Symbol.toStringTag"}
)

Well-known symbols.

View Source 
var ErrInterrupted = errors.New("js: interrupted")

ErrInterrupted is what a realm's code panics with once Interrupt is called.

View Source 
var Hole = hole

Hole is the element of an elision in an array literal.

View Source 
var UnknownPrivate = &PrivateName{Description: "#unknown"}

UnknownPrivate stands for a private name the compiler couldn't find.

Functions

func CopyDataProperties 

func CopyDataProperties(target *Object, src Value)

CopyDataProperties is object spread: {...src}.

func DefineField 

func DefineField(obj Value, key PropKey, v Value)

DefineField is a class field: an own, enumerable property.

func Delete 

func Delete(v Value, key PropKey) bool

Delete is the delete operator on v[key].

func FromUnits 

func FromUnits(u []uint16) string

FromUnits encodes UTF-16 code units, pairing surrogates where they pair.

func HasPrivate added in v1.8.0 

func HasPrivate(obj Value, name *PrivateName) bool

HasPrivate is #name in obj.

func In 

func In(key Value, obj Value) bool

In is the in operator.

func InheritStatics 

func InheritStatics(ctor *Object, parent Value)

InheritStatics makes a subclass's constructor inherit the parent's statics.

func InstanceOfProto added in v1.6.0 

func InstanceOfProto(v Value, proto *Object) bool

InstanceOfProto reports whether proto is on v's prototype chain.

func IsArray 

func IsArray(v Value) bool

IsArray is Array.isArray.

func IsConstructor 

func IsConstructor(v Value) bool

IsConstructor reports whether new can call v.

func IsNullish 

func IsNullish(v Value) bool

IsNullish reports whether v is undefined or null.

func IsPlainArray added in v1.8.0 

func IsPlainArray(o *Object) bool

IsPlainArray reports whether o is an array whose length is there without running code: an array, not a proxy of one.

func Itoa 

func Itoa(i int) string

Itoa formats an integer index as a property key.

func Join 

func Join(a []Value, sep string) string

Join is Array.prototype.join: undefined and null become "".

func LooseEquals 

func LooseEquals(a, b Value) bool

LooseEquals is ==.

func Nullish 

func Nullish(v Value) bool

Nullish is a ?? b's test.

func NumberToString 

func NumberToString(x float64) string

NumberToString is Number::toString(x) with radix 10.

func PrivateAccessor 

func PrivateAccessor(obj Value, name *PrivateName, get, set Value)

PrivateAccessor adds a private getter or setter.

func PrivateDefine 

func PrivateDefine(obj Value, name *PrivateName, v Value)

PrivateDefine adds a private field or method to an object.

func PrivateSet 

func PrivateSet(obj Value, name *PrivateName, v Value)

PrivateSet writes obj.#name.

func QuoteJSON 

func QuoteJSON(b *strings.Builder, s string)

QuoteJSON writes s as a JSON string, as JSON.stringify quotes it: lone surrogates become \u escapes.

func RequireObjectCoercible 

func RequireObjectCoercible(v Value)

RequireObjectCoercible throws for destructuring undefined or null.

func SameValue 

func SameValue(a, b Value) bool

SameValue is Object.is.

func SameValueZero 

func SameValueZero(a, b Value) bool

SameValueZero is SameValueZero, for includes and Map keys.

func Set 

func Set(v Value, key PropKey, val Value)

Set is v[key] = val in strict mode code.

func SetProtoFromLiteral 

func SetProtoFromLiteral(o *Object, v Value)

SetProtoFromLiteral is __proto__: v in an object literal.

func SetV 

func SetV(v Value, k Value, val Value)

SetV is v[k] = val where k is any value.

func StrictEquals 

func StrictEquals(a, b Value) bool

StrictEquals is ===.

func StringToNumber 

func StringToNumber(s string) float64

StringToNumber is StringToNumber: decimal, 0x/0o/0b integers, Infinity, and the empty string as 0.

func SuperSet 

func SuperSet(proto *Object, key PropKey, v Value, this Value)

SuperSet is super[key] = v.

func ToDisplay 

func ToDisplay(v Value) string

ToDisplay describes a value for error messages, without running any code.

func ToFixed 

func ToFixed(x float64, d int) string

ToFixed is Number.prototype.toFixed.

func ToGo 

func ToGo(v Value) any

ToGo converts a primitive to Go: nil, bool, int (for whole numbers), float64 or string. Objects become their string conversion's result.

func ToInt32 

func ToInt32(v Value) int32

ToInt32 is ToInt32, for the bitwise operators.

func ToIntegerOrInfinity 

func ToIntegerOrInfinity(v Value) float64

ToIntegerOrInfinity is ToIntegerOrInfinity.

func ToNumber 

func ToNumber(v Value) float64

ToNumber is the abstract operation ToNumber.

func ToString 

func ToString(v Value) string

ToString is the abstract operation ToString.

func ToUint32 

func ToUint32(v Value) uint32

ToUint32 is ToUint32.

func TrimJSSpace 

func TrimJSSpace(s string) string

TrimJSSpace trims what String.prototype.trim trims.

func Truthy 

func Truthy(v Value) bool

Truthy is ToBoolean.

func Typeof 

func Typeof(v Value) string

Typeof is the typeof operator.

func Units 

func Units(s string) []uint16

Units decodes s into UTF-16 code units.

Types

type Boxer added in v1.15.0 

type Boxer struct {
	// contains filtered or unexported fields
}

Boxer hands out the boxes of strings and numbers from slabs. Putting a string or a float64 in an interface allocates a box for it, 16 or 8 bytes, which is most of a render's allocations; a Boxer makes one allocation per slab instead. The Values are ordinary interfaces, and a slab stays alive while any of its Values does, which during a render is the render.

A Boxer belongs to one goroutine at a time, as a Realm does.

func (*Boxer) Num added in v1.15.0 

func (b *Boxer) Num(f float64) Value

Num returns f as a Value; small integers need no box at all.

func (*Boxer) Str added in v1.15.0 

func (b *Boxer) Str(s string) Value

Str returns s as a Value.

type FnInfo 

type FnInfo struct {
	Name   string
	Length int
	// Src, Module, Start and End locate the source text: UTF-16 offsets
	// into one module of Src.
	Src                *Sources
	Module, Start, End int
}

FnInfo is what a function knows about itself: its name, its length (the number of declared parameters) and, for compiled functions, its source text, which toString returns. Compiled code has one per function in its source, shared by every closure made from it.

func (*FnInfo) Source 

func (f *FnInfo) Source() string

Source is the function's source text, or "" for a built-in.

type Gen 

type Gen struct {
	// contains filtered or unexported fields
}

Gen is a generator object's state.

func (*Gen) AsyncYield added in v1.6.0 

func (g *Gen) AsyncYield(v Value) Value

AsyncYield is yield in an async generator: the value is awaited first.

func (*Gen) Await 

func (g *Gen) Await(v Value) Value

Await is an await expression: the body waits for v to settle, and gets its value, or its reason thrown.

func (*Gen) Yield 

func (g *Gen) Yield(v Value) Value

Yield is a yield expression: it hands v to the consumer and returns what the next call to next passes.

func (*Gen) YieldStar 

func (g *Gen) YieldStar(v Value) Value

YieldStar is yield* v.

type GlobalRef 

type GlobalRef struct {
	// contains filtered or unexported fields
}

GlobalRef caches a global's value at one place in compiled code.

type IC 

type IC struct {
	// contains filtered or unexported fields
}

IC is one access site's cache.

type Object 

type Object struct {

	// Internal slots: Map and Set data, a RegExp, a Date's time, a boxed primitive.
	Internal any
	// Class is the kind of built-in object, such as "Map" or "Error", for
	// Object.prototype.toString and instanceof checks of built-ins.
	Class string
	// contains filtered or unexported fields
}

Object is a JavaScript object. Functions, arrays and the built-in objects with internal slots (Map, Set, RegExp, Date, errors) are objects with the matching fields set.

func AsObject 

func AsObject(v Value) *Object

AsObject asserts that a compiled function expression is a function object.

func ClassParentProto 

func ClassParentProto(parent Value) *Object

ClassParentProto is the prototype of a class's instances' prototype: the superclass's prototype, or null for extends null.

func NewNamespace 

func NewNamespace() *Object

NewNamespace makes a module namespace object.

func NewObject 

func NewObject(proto *Object) *Object

NewObject makes an ordinary object with the given prototype (nil for none).

func OrdinaryCreateFromConstructor 

func OrdinaryCreateFromConstructor(newTarget *Object, fallback *Object) *Object

OrdinaryCreateFromConstructor makes the object a constructor builds: its prototype is newTarget.prototype, or fallback.

func ProtoOf 

func ProtoOf(v Value) *Object

ProtoOf is an object's prototype, for super in object literal methods.

func WithInfo 

func WithInfo(o *Object, info *FnInfo) *Object

WithInfo sets o's info and returns o, for compiled code.

func (*Object) ArrayElements added in v1.8.0 

func (o *Object) ArrayElements() ([]Value, bool)

ArrayElements is an array's elements, when it's a plain array: no holes, no proxy. ok is false otherwise.

func (*Object) Define 

func (o *Object) Define(key PropKey, v Value)

Define makes an own, enumerable, writable data property, as an object literal does.

func (*Object) DefineAccessor 

func (o *Object) DefineAccessor(key PropKey, get, set *Object, enumerable bool)

DefineAccessor makes a getter and/or setter property. Object literals' accessors are enumerable; classes' are not.

func (*Object) DefineHidden 

func (o *Object) DefineHidden(key PropKey, v Value)

DefineHidden makes an own, non-enumerable data property, as built-ins and class methods have.

func (*Object) DefineProperty 

func (o *Object) DefineProperty(key PropKey, desc *Object)

DefineProperty is Object.defineProperty with a parsed descriptor.

func (*Object) Delete 

func (o *Object) Delete(key PropKey) bool

Delete is the delete operator.

func (*Object) Elems 

func (o *Object) Elems() []Value

Elems returns an array's elements, which the caller may read but not keep.

func (*Object) EnumerableOwn 

func (o *Object) EnumerableOwn(fn func(key string, v Value))

EnumerableOwn calls fn for each enumerable own string-keyed property, in order, as Object.keys, for…in over own keys and object spread do.

func (*Object) Freeze 

func (o *Object) Freeze()

Freeze is Object.freeze.

func (*Object) Get 

func (o *Object) Get(key PropKey) Value

Get is [[Get]] with o as the receiver.

func (*Object) GetFrom 

func (o *Object) GetFrom(key PropKey, receiver Value) Value

GetFrom is [[Get]] with another receiver, for getters on prototypes and for primitives' methods.

func (*Object) GetOwn 

func (o *Object) GetOwn(key PropKey) (Value, bool)

GetOwn returns an own data property's value without running getters.

func (*Object) Has 

func (o *Object) Has(key PropKey) bool

Has is the in operator.

func (*Object) HasOwn 

func (o *Object) HasOwn(key PropKey) bool

HasOwn is Object.hasOwn.

func (*Object) HasOwnString added in v1.8.0 

func (o *Object) HasOwnString(key string) (has, ok bool)

HasOwnString is Object.prototype.hasOwnProperty for a string key, for ordinary objects; ok is false for proxies and exotic objects, where it could run code or needs the full algorithm.

func (*Object) IsCallable 

func (o *Object) IsCallable() bool

IsCallable reports whether o is a function.

func (*Object) IsFrozen 

func (o *Object) IsFrozen() bool

IsFrozen is Object.isFrozen.

func (*Object) OwnKeys 

func (o *Object) OwnKeys(onlyEnumerable, withSymbols bool) []PropKey

OwnKeys lists own property keys in JavaScript's order: array indexes ascending, then strings in creation order, then symbols.

func (*Object) PlainEach added in v1.15.0 

func (o *Object) PlainEach(fn func(key string, v Value)) (ok bool)

PlainEach calls fn with each own enumerable string-keyed property of an ordinary object, in property order, without allocating; ok is false where PlainEntries would be, and for objects with integer keys, which come first in property order.

func (*Object) PlainEntries added in v1.8.0 

func (o *Object) PlainEntries() (keys []string, vals []Value, ok bool)

PlainEntries is Object.keys(o) with each key's value, when reading them can't run code: o is an ordinary object (not an array, typed array or proxy) whose own string-keyed properties are all data properties. ok is false otherwise, for code with a fast path for plain objects.

func (*Object) Proto 

func (o *Object) Proto() *Object

Proto is the object's prototype, or nil.

func (*Object) Push 

func (o *Object) Push(v ...Value)

Push appends to an array.

func (*Object) Set 

func (o *Object) Set(key PropKey, v Value)

Set is [Set] in strict mode code: it throws where sloppy code would silently fail.

func (*Object) SetConstruct 

func (o *Object) SetConstruct(fn func(args []Value, newTarget *Object) Value)

SetConstruct makes an existing function a constructor.

func (*Object) SetFrom 

func (o *Object) SetFrom(key PropKey, v Value, receiver Value)

SetFrom is [Set] with a receiver.

func (*Object) SetInfo 

func (o *Object) SetInfo(info *FnInfo)

SetInfo describes a function made another way, such as a class.

func (*Object) SetProto 

func (o *Object) SetProto(p *Object)

SetProto changes the prototype. The shape follows: shapes know their prototype.

type PrivateName 

type PrivateName struct{ Description string }

PrivateName is a class's #name; each evaluation of the class makes new ones.

func NewPrivateName 

func NewPrivateName(desc string) *PrivateName

NewPrivateName makes a private name.

type PropKey 

type PropKey = any

PropKey is a property key: a string or a *Symbol.

func ToPropertyKey 

func ToPropertyKey(v Value) PropKey

ToPropertyKey is ToPropertyKey.

type Realm 

type Realm struct {

	// The intrinsic objects.
	ObjectPrototype, FunctionPrototype, ArrayPrototype, StringPrototype *Object
	NumberPrototype, BooleanPrototype, SymbolPrototype, ErrorPrototype  *Object
	IteratorPrototype, DatePrototype, RegExpPrototype, PromisePrototype *Object

	ArrayBufferPrototype, TypedArrayPrototype, DataViewPrototype *Object
	GeneratorPrototype, GeneratorFunctionPrototype               *Object
	ObjectCtor, FunctionCtor, ArrayCtor, StringCtor, NumberCtor  *Object
	BooleanCtor, SymbolCtor                                      *Object
	Error, TypeError, RangeError, SyntaxError, ReferenceError    *Object

	BigIntPrototype         *Object
	AsyncIteratorPrototype  *Object
	AsyncGeneratorPrototype *Object

	// Global is globalThis.
	Global *Object
	// contains filtered or unexported fields
}

A Realm is a world of JavaScript objects: its own built-ins, globalThis and module state. Realms share nothing that changes, so each can run on its own goroutine; one realm runs one thing at a time.

func NewRealm 

func NewRealm() *Realm

NewRealm makes a realm with the built-ins and an empty globalThis.

func (*Realm) Add 

func (rt *Realm) Add(a, b Value) Value

Add is the + operator.

func (*Realm) ArrayValues 

func (rt *Realm) ArrayValues() Value

ArrayValues is Array.prototype.values, to tell built-in iteration apart.

func (*Realm) AsyncIterate added in v1.6.0 

func (rt *Realm) AsyncIterate(v Value) func() Value

AsyncIterate starts a for await: it returns the function that gets the next result's promise. A sync iterable is wrapped, its values awaited.

func (*Realm) CallIC 

func (rt *Realm) CallIC(c *IC, obj Value, key string, args ...Value) Value

CallIC is obj.key(…args) with a cache.

func (*Realm) CallMethod 

func (rt *Realm) CallMethod(obj Value, key PropKey, args ...Value) Value

CallMethod is obj[key](...args), with obj as this.

func (*Realm) CallMethodV 

func (rt *Realm) CallMethodV(obj Value, key Value, args ...Value) Value

CallMethodV is obj[key](...args) with a computed key.

func (*Realm) CompareStrings 

func (rt *Realm) CompareStrings(a, b string) int

CompareStrings orders strings by UTF-16 code units, as < does.

func (*Realm) Concat 

func (rt *Realm) Concat(a, b string) string

Concat is a + b for strings.

func (*Realm) CopyDataPropertiesExcluding 

func (rt *Realm) CopyDataPropertiesExcluding(src Value, excluded []PropKey) *Object

CopyDataPropertiesExcluding is an object pattern's rest element.

func (*Realm) DropJobs 

func (rt *Realm) DropJobs()

DropJobs forgets the queued jobs.

func (*Realm) DynamicImport added in v1.6.0 

func (rt *Realm) DynamicImport(load func() Value) *Object

DynamicImport is import() of a compiled module: a promise that loads the module in a job, as bundlers compile import(). A render never runs the job, in QuickJS or natively.

func (*Realm) ExportLive 

func (rt *Realm) ExportLive(ns *Object, name string, get func() Value)

ExportLive adds a live binding to a namespace.

func (*Realm) FailedImport added in v1.6.0 

func (rt *Realm) FailedImport(spec Value) *Object

FailedImport is import() of a module no bundle has, such as a Node built-in: a promise that rejects in a job.

func (*Realm) ForInKeys 

func (rt *Realm) ForInKeys(v Value) func() (Value, bool)

ForInKeys returns a for…in's next function: enumerable string keys of the object and its prototypes, each once.

func (*Realm) ForOf 

func (rt *Realm) ForOf(v Value, fn func(Value) bool)

ForOf runs fn for each value of a for…of over v, until fn returns false.

func (*Realm) Get 

func (rt *Realm) Get(v Value, key PropKey) Value

Get is v[key] for any value: objects, and primitives through their prototypes.

func (*Realm) GetIC 

func (rt *Realm) GetIC(c *IC, v Value, key string) Value

GetIC is obj.key with a cache.

func (*Realm) GetOptional 

func (rt *Realm) GetOptional(v Value, key PropKey) Value

GetOptional is v?.[key]: undefined when v is nullish.

func (*Realm) GetV 

func (rt *Realm) GetV(v Value, k Value) Value

GetV is v[k] where k is any value, with a fast path for array indexes.

func (*Realm) GlobalGet 

func (rt *Realm) GlobalGet(name string) Value

GlobalGet reads an undeclared identifier from globalThis.

func (*Realm) GlobalGetCached 

func (rt *Realm) GlobalGetCached(c *GlobalRef, name string) Value

GlobalGetCached is GlobalGet with a cache, valid until globalThis's own properties change. Accessors and inherited properties aren't cached.

func (*Realm) GlobalSet 

func (rt *Realm) GlobalSet(name string, v Value)

GlobalSet assigns an undeclared identifier, which strict mode only allows when globalThis has it.

func (*Realm) Greater 

func (rt *Realm) Greater(a, b Value) bool

Greater is >.

func (*Realm) GreaterEq 

func (rt *Realm) GreaterEq(a, b Value) bool

GreaterEq is >=.

func (*Realm) HostFunc 

func (rt *Realm) HostFunc(name string, fn func(args []any) (any, error))

HostFunc makes a global function that calls Go, as the QuickJS renderer's host functions do: arguments arrive as strings, numbers (int when whole), bools or nil, and the result goes back the same way. An error becomes a thrown Error.

func (*Realm) Index16 

func (rt *Realm) Index16(s, sub string, from int) int

Index16 is s.indexOf(sub, from).

func (*Realm) InstanceOf 

func (rt *Realm) InstanceOf(v Value, ctor Value) bool

InstanceOf is instanceof.

func (*Realm) Interrupt 

func (rt *Realm) Interrupt()

Interrupt stops the realm's running code at its next call or loop turn; it may be called from any goroutine. The realm can't be used after.

func (*Realm) Iterate 

func (rt *Realm) Iterate(v Value) func() (Value, bool)

Iterate returns a for…of's next function.

func (*Realm) Len16 

func (rt *Realm) Len16(s string) int

Len16 is a string's length in UTF-16 code units.

func (*Realm) Less 

func (rt *Realm) Less(a, b Value) bool

Less is <.

func (*Realm) LessEq 

func (rt *Realm) LessEq(a, b Value) bool

LessEq is <=.

func (*Realm) NewArguments 

func (rt *Realm) NewArguments(args []Value) *Object

NewArguments is a function's arguments object.

func (*Realm) NewArray 

func (rt *Realm) NewArray(elems []Value) *Object

NewArray makes an array holding elems (which it keeps).

func (*Realm) NewArrayBuffer 

func (rt *Realm) NewArrayBuffer(data []byte) *Object

NewArrayBuffer makes an ArrayBuffer holding data.

func (*Realm) NewArrayWithHoles 

func (rt *Realm) NewArrayWithHoles(elems []Value) *Object

NewArrayWithHoles makes an array literal with elisions, like [1, , 3]: Hole marks each missing element.

func (*Realm) NewAsyncFunction 

func (rt *Realm) NewAsyncFunction(name string, length int, call func(this Value, args []Value) func(*Gen) Value) *Object

NewAsyncFunction makes an async function. call binds the parameters and returns the body.

func (*Realm) NewAsyncGeneratorFunction added in v1.6.0 

func (rt *Realm) NewAsyncGeneratorFunction(name string, length int, call func(this Value, args []Value) func(*Gen) Value) *Object

NewAsyncGeneratorFunction makes an async generator function.

func (*Realm) NewConstructor 

func (rt *Realm) NewConstructor(name string, length int, call func(this Value, args []Value) Value, construct func(args []Value, newTarget *Object) Value, proto *Object) *Object

NewConstructor makes a function that new can call, with a prototype object whose constructor is the function. construct receives the new target, for subclasses.

func (*Realm) NewDate 

func (rt *Realm) NewDate(ms float64) *Object

NewDate makes a Date for a time value in milliseconds.

func (*Realm) NewFunction 

func (rt *Realm) NewFunction(name string, length int, fn func(this Value, args []Value) Value) *Object

NewFunction makes a function object.

func (*Realm) NewFunctionOf 

func (rt *Realm) NewFunctionOf(info *FnInfo, fn func(this Value, args []Value) Value) *Object

NewFunctionOf makes a function object described by info.

func (*Realm) NewGeneratorFunction 

func (rt *Realm) NewGeneratorFunction(name string, length int, call func(this Value, args []Value) func(*Gen) Value) *Object

NewGeneratorFunction makes a generator function. call runs when it's called: it binds the parameters and returns the body.

func (*Realm) NewIterator 

func (rt *Realm) NewIterator(next func() (Value, bool)) *Object

NewIterator makes an iterator object from a next function.

func (*Realm) NewObjectFrom added in v1.8.0 

func (rt *Realm) NewObjectFrom(keys []PropKey, vals []Value) *Object

NewObjectFrom makes the object JSON.parse makes for these members, in order: a repeated key's last value wins. keys and vals are copied.

func (*Realm) NewPlainObject 

func (rt *Realm) NewPlainObject() *Object

NewPlainObject makes an object like an object literal does.

func (*Realm) NewProxy 

func (rt *Realm) NewProxy(target, handler *Object) *Object

NewProxy is new Proxy(target, handler).

func (*Realm) NewRegExp 

func (rt *Realm) NewRegExp(source, flags string) *Object

NewRegExp compiles a regular expression literal or new RegExp(source, flags).

func (*Realm) NonArrow 

func (rt *Realm) NonArrow(f *Object) *Object

NonArrow makes a function declaration or expression constructible, as non-arrow functions are.

func (*Realm) NonArrowNewTarget added in v1.6.0 

func (rt *Realm) NonArrowNewTarget(f *Object) *Object

NonArrowNewTarget is NonArrow for a function that reads new.target: its construct hands the new target over, which the function's first statement takes (TakeNewTarget).

func (*Realm) Num added in v1.15.0 

func (rt *Realm) Num(f float64) Value

Num returns f as a Value, boxed from the realm's slabs.

func (*Realm) Obj 

func (rt *Realm) Obj(kv ...Value) *Object

Obj makes an object literal from keys and values.

func (*Realm) ObjectToString 

func (rt *Realm) ObjectToString(v Value) string

ObjectToString is Object.prototype.toString.

func (*Realm) ParseJSON 

func (rt *Realm) ParseJSON(s string) (Value, error)

ParseJSON is JSON.parse without a reviver.

func (*Realm) PushPlain added in v1.8.0 

func (rt *Realm) PushPlain(ic *IC, v, x Value) bool

PushPlain is v.push(x) for an array whose push is the built-in one, for Go code that appends where JavaScript would call push. It reports false, doing nothing, for anything else, which the caller then calls.

func (*Realm) RegExpLiteral 

func (rt *Realm) RegExpLiteral(source, flags string) Value

RegExpLiteral evaluates a regular expression literal: a new object each time, sharing the compiled pattern.

func (*Realm) Remaining 

func (rt *Realm) Remaining(next func() (Value, bool)) *Object

Remaining collects an iterator's remaining values, for [...rest].

func (*Realm) Reset 

func (rt *Realm) Reset()

Reset clears what an interrupted or failed call left behind, for the next call: the argument stack, the call depth and queued jobs.

func (*Realm) Rest 

func (rt *Realm) Rest(args []Value, i int) *Object

Rest is a rest parameter: the arguments from i on.

func (*Realm) RunJobs 

func (rt *Realm) RunJobs()

RunJobs runs queued jobs, and the jobs they queue, until none are left.

func (*Realm) SetIC 

func (rt *Realm) SetIC(c *IC, obj Value, key string, v Value)

SetIC is obj.key = v with a cache, for a writable own property or for adding one.

func (*Realm) Slice16 

func (rt *Realm) Slice16(s string, start, end int) string

Slice16 is s.slice(start, end) after both are clamped to [0, len].

func (*Realm) Spread 

func (rt *Realm) Spread(v Value) []Value

Spread collects the values of v, for [...v] and f(...v).

func (*Realm) Str added in v1.15.0 

func (rt *Realm) Str(s string) Value

Str returns s as a Value, boxed from the realm's slabs.

func (*Realm) Stringify 

func (rt *Realm) Stringify(v, replacer, space Value) (string, bool)

Stringify is JSON.stringify; ok is false when the result is undefined.

func (*Realm) TakeNewTarget added in v1.6.0 

func (rt *Realm) TakeNewTarget() Value

TakeNewTarget is new.target in a function: the new target its construct handed over, or undefined for a call.

func (*Realm) TemplateObject 

func (rt *Realm) TemplateObject(site int, cooked []Value, raw []string) Value

TemplateObject is a tagged template's strings array, the same object every time its call site runs.

func (*Realm) Tick 

func (rt *Realm) Tick()

Tick is compiled into every loop: it stops interrupted code.

func (*Realm) ToObject 

func (rt *Realm) ToObject(v Value) *Object

ToObject boxes primitives, for property access and Object(...).

func (*Realm) TreeShaken 

func (rt *Realm) TreeShaken(spec, name string) Value

TreeShaken stands for a binding imported from a module the bundler left out, as nothing the bundle runs uses it: it can be passed around, but using it raises Unsupported, so the page falls back to the engine.

func (*Realm) Try 

func (rt *Realm) Try(body func() (int, Value), catch func(Value) (int, Value), finally func() (int, Value)) (ctl int, val Value)

Try runs try…catch…finally. Each part returns how it ended: CtlNone to carry on, or a return, break or continue with its value (a break or continue carries the target's number).

func (*Realm) TypeofGlobal 

func (rt *Realm) TypeofGlobal(name string) string

TypeofGlobal is typeof of an undeclared identifier.

func (*Realm) UnitAt 

func (rt *Realm) UnitAt(s string, i int) int

UnitAt is s.charCodeAt(i), or -1 out of range.

type Shape 

type Shape struct {
	// contains filtered or unexported fields
}

Shape is the layout of objects' own properties.

type Sources 

type Sources struct {
	// contains filtered or unexported fields
}

Sources is the source text of compiled modules, for Function.prototype .toString: gzipped JSON, an array of each module's code, unpacked when first needed.

func NewSources 

func NewSources(gz string) *Sources

NewSources holds gzipped sources.

func (*Sources) Module 

func (s *Sources) Module(i int) string

Module is the code of module i.

type Symbol 

type Symbol struct{ Description string }

Symbol is a JavaScript symbol. Each one is distinct.

type Throw 

type Throw struct {
	// Value is what was thrown; nil for a runtime error not yet made.
	Value   Value
	Kind    string // the error constructor's name, for a runtime error
	Message string
}

Throw is a JavaScript exception in flight: compiled code panics with it, and try/catch recovers it.

The runtime's own errors, such as a TypeError, start with just a kind and a message: their error object is made in the realm that catches them, by In. Raising them needs no realm, so neither do the value operations that can fail.

func RangeErrorf 

func RangeErrorf(format string, args ...any) *Throw

RangeErrorf makes a RangeError exception.

func ReferenceErrorf 

func ReferenceErrorf(format string, args ...any) *Throw

ReferenceErrorf makes a ReferenceError exception.

func SyntaxErrorf 

func SyntaxErrorf(format string, args ...any) *Throw

SyntaxErrorf makes a SyntaxError exception.

func ThrowValue 

func ThrowValue(v Value) *Throw

ThrowValue makes a throw statement's panic.

func TypeErrorf 

func TypeErrorf(format string, args ...any) *Throw

TypeErrorf makes a TypeError exception.

func URIErrorf 

func URIErrorf(format string, args ...any) *Throw

URIErrorf makes a URIError exception.

func (*Throw) Error 

func (t *Throw) Error() string

func (*Throw) In 

func (t *Throw) In(r *Realm) Value

In returns the thrown value, making a runtime error's object in r.

type Unsupported 

type Unsupported struct{ What string }

Unsupported is raised when compiled code meets something the compiler handles only partly; the request falls back to the JavaScript engine.

func NotSupported 

func NotSupported(format string, args ...any) *Unsupported

NotSupported panics with an Unsupported.

func (*Unsupported) Error 

func (u *Unsupported) Error() string

type Value 

type Value = any

Value is a JavaScript value. 

var (
	Inf     Value = math.Inf(1)
	NegInf  Value = math.Inf(-1)
	NaN     Value = math.NaN()
	NegZero Value = math.Copysign(0, -1)
)

Number constants that have no Go literal. 

var (
	Undefined Value = undefinedType{}
	Null      Value = nullType{}
)

The two values that aren't objects or primitives of a Go type.

func Arg 

func Arg(args []Value, i int) Value

Arg returns args[i], or undefined.

func BigIntLit added in v1.6.0 

func BigIntLit(digits string) Value

BigIntLit is a BigInt literal's value, from its digits.

func BitAnd 

func BitAnd(a, b Value) Value

BitAnd is &.

func BitNot 

func BitNot(a Value) Value

BitNot is ~.

func BitOr 

func BitOr(a, b Value) Value

BitOr is |.

func BitXor 

func BitXor(a, b Value) Value

BitXor is ^.

func Box 

func Box(f float64) Value

Box makes a number a Value, without allocating for small integers.

func Call 

func Call(f Value, this Value, args ...Value) Value

Call calls f with a this value.

func CheckThis 

func CheckThis(v Value) Value

CheckThis reads this in a derived constructor, which super() sets.

func Construct 

func Construct(f Value, args ...Value) Value

Construct is the new operator.

func ConstructWith 

func ConstructWith(f Value, newTarget *Object, args ...Value) Value

ConstructWith is construct with an explicit new target, for super(...).

func Dec 

func Dec(v Value) Value

Dec is x - 1 for x-- and --x.

func Div 

func Div(a, b Value) Value

Div is the / operator.

func Fail 

func Fail(what string) Value

Fail is compiled in place of what the compiler can't compile.

func FromGo 

func FromGo(v any) Value

FromGo converts a Go value to a primitive Value.

func Inc 

func Inc(v Value) Value

Inc is x + 1 for x++ and ++x.

func ListFromArrayLike 

func ListFromArrayLike(v Value) []Value

ListFromArrayLike turns an array or array-like object into arguments.

func MissingExport 

func MissingExport(module, name string) Value

MissingExport stands for an import of a name the module doesn't export.

func MissingImport 

func MissingImport(spec, name string) Value

MissingImport stands for a binding imported from a module the IR doesn't have; reading it raises Unsupported.

func Mod 

func Mod(a, b Value) Value

Mod is the % operator: the result has the dividend's sign.

func Mul 

func Mul(a, b Value) Value

Mul is the * operator.

func Neg 

func Neg(a Value) Value

Neg is unary -.

func Num 

func Num[T ~int | ~int8 | ~int16 | ~int32 | ~int64 | ~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 | ~float32 | ~float64](n T) Value

Num makes a number from any Go number, for generated code.

func Plus 

func Plus(a Value) Value

Plus is unary +.

func Pow 

func Pow(a, b Value) Value

Pow is **, where JavaScript differs from math.Pow: 1 ** NaN and (-1) ** ±Infinity are NaN.

func PrivateGet 

func PrivateGet(obj Value, name *PrivateName) Value

PrivateGet reads obj.#name.

func PrivateIn 

func PrivateIn(name *PrivateName, obj Value) Value

PrivateIn is #name in obj.

func Shl 

func Shl(a, b Value) Value

Shl is <<.

func Shr 

func Shr(a, b Value) Value

Shr is >>.

func Sub 

func Sub(a, b Value) Value

Sub is the - operator.

func SuperGet 

func SuperGet(proto *Object, key PropKey, this Value) Value

SuperGet is super[key] in a method.

func ToPrimitive 

func ToPrimitive(v Value, hint string) Value

ToPrimitive with a hint of "default", "number" or "string".

func ToStringValue 

func ToStringValue(v Value) Value

ToStringValue is ToString as a Value: a string comes back as it is, without the allocation of boxing it again.

func UShr 

func UShr(a, b Value) Value

UShr is >>>.

func V 

func V(v Value) Value

V is v. Compiled code wraps a variable read in it to keep the read in order with the calls around it (see internal/native).

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