API reference / @jsprismarine/molang

@jsprismarine/molang

Molang parser, compiler and evaluator for Bedrock behavior packs. Parses the full Molang grammar with a Pratt parser, compiles each expression once per (source, version) into a JavaScript closure, and evaluates it over a typed scope (entity, block permutation, item, world, placement, context.*, variable.*, temp.*).

import { Molang } from '@jsprismarine/molang';

const molang = new Molang();
const compiled = molang.compile('query.is_baby ? 0.02 : 0.001', { minEngineVersion: [1, 21, 0] });
const value = compiled.evaluate({ entity: myEntityContext });

Operator precedence is versioned by the containing pack's min_engine_version, matching the engine's rule changes at 1.18.10 (ternary associativity) and 1.18.20 (&& over ||, comparison over equality). Unknown query.* and math.* identifiers are reported through the compile diagnostics and evaluate to 0.0 at run time, as the engine does.

Examples

These expressions are exported as MOLANG_EXAMPLES, each with the scopes it is shown under and the value it produces. The test suite compiles every one with no diagnostics and checks the values, and fails if this section drifts from the list, so they are safe to copy.

import { MOLANG_EXAMPLES, Molang } from '@jsprismarine/molang';

const molang = new Molang();
for (const example of MOLANG_EXAMPLES) {
    const compiled = molang.compile(example.source);
    for (const { label, scope, expected } of example.cases) {
        console.log(example.title, label, compiled.evaluate(scope), expected);
    }
}

A chance that depends on age

A ternary picks between two numbers, as an ambient sound probability does.

molang

query.is_baby ? 0.02 : 0.001

a baby: 0.02; an adult: 0.001.

A value kept in range

The math functions take and return numbers; clamp(value, min, max) bounds a variant index.

molang

math.clamp(query.variant, 0, 3)

variant 2: 2; variant 9: 3.

A spawn condition

Booleans are 1 and 0, so conditions combine with &&, || and !.

molang

query.head_is_in_water && !query.is_on_ground

swimming: 1; standing in the shallows: 0.

A string property

Strings compare with == and !=, and query.property reads an entity property.

molang

query.property('example:color') == 'red'

red: 1; blue: 0.

Worn-out tools

An item expression reads durability; the result is 1 once less than a tenth is left.

molang

query.remaining_durability / query.max_durability < 0.1

almost broken: 1; nearly new: 0.

Interpolating between two numbers

math.lerp(start, end, t) blends linearly.

molang

math.lerp(10, 20, 0.25)

no scope needed: 12.5.

A reward that grows with level

Arithmetic follows the usual precedence, so the multiplication happens before the cap.

molang

math.min(10 + query.player_level * 5, 100)

level 4: 30; level 40: 100.

A terrain condition

Worldgen queries take coordinates and read the placement context.

molang

query.heightmap(0, 0) > 62

above sea level: 1; under water: 0.

A complex expression with a loop

Statements end in ;, v. is variable., and a complex expression yields what return gives it.

molang

v.total = 0; loop(5, { v.total = v.total + 2; }); return v.total;

five rounds of two: 10.

Stopping a loop early

break leaves the loop; the loop is capped at 1024 rounds either way.

molang

v.n = 0; loop(100, { v.n = v.n + 1; (v.n >= 7) ? break; }); return v.n;

stops at seven: 7.

Classes

Interfaces

ArrowNode

Defined in: ast.ts:63

The arrow operator left->right; evaluates right against the entity left resolves to.

Properties

kind

kind: "arrow"

Defined in: ast.ts:64

left

left: ExpressionNode

Defined in: ast.ts:65

right

right: ExpressionNode

Defined in: ast.ts:66

AssignNode

Defined in: ast.ts:77

An assignment to variable.* or temp.* storage.

Properties

kind

kind: "assign"

Defined in: ast.ts:78

target

target: ReferenceNode

Defined in: ast.ts:79

value

value: ExpressionNode

Defined in: ast.ts:80

BinaryNode

Defined in: ast.ts:47

A binary operation.

Properties

kind

kind: "binary"

Defined in: ast.ts:48

left

left: ExpressionNode

Defined in: ast.ts:50

operator

operator: BinaryOperator

Defined in: ast.ts:49

right

right: ExpressionNode

Defined in: ast.ts:51

BlockContext

Defined in: scope.ts:54

Block permutation state for query.block_state and tag queries on blocks.

Methods

blockState()?

optional blockState(name): string | number | boolean | undefined

Defined in: scope.ts:56

The value of the named block state, or undefined when the permutation lacks it.

Parameters

name

string

Returns

string | number | boolean | undefined

tags()?

optional tags(): readonly string[]

Defined in: scope.ts:58

The block's tags, for query.any_tag and query.all_tags.

Returns

readonly string[]

BlockNode

Defined in: ast.ts:98

A braced statement list { a = 1; b = 2; }.

Properties

kind

kind: "block"

Defined in: ast.ts:99

statements

statements: readonly StatementNode[]

Defined in: ast.ts:100

CallNode

Defined in: ast.ts:30

A call such as math.clamp(a, b, c) or query.anger_level(this).

Properties

args

args: readonly ExpressionNode[]

Defined in: ast.ts:33

callee

callee: ReferenceNode

Defined in: ast.ts:32

kind

kind: "call"

Defined in: ast.ts:31

CompileOptions

Defined in: Molang.ts:10

Options for one compilation.

Properties

minEngineVersion?

optional minEngineVersion?: EngineVersion

Defined in: Molang.ts:15

The min_engine_version of the pack that contains the expression. Selects the versioned precedence and evaluation rules; the latest rules apply when omitted.

CompiledMolang

Defined in: compiler.ts:74

A compiled Molang expression: the parse diagnostics and a closure to evaluate it.

Properties

ast?

optional ast?: ProgramNode

Defined in: compiler.ts:78

The parsed program, or undefined when the source failed to parse.

diagnostics

diagnostics: readonly Diagnostic[]

Defined in: compiler.ts:80

Problems found at parse or bind time; the closure still evaluates, erroring parts as 0.

evaluate

evaluate: (scope) => MolangValue

Defined in: compiler.ts:82

Evaluates the expression over the scope. Booleans come back as 0 and 1.

Parameters

scope

MolangScope

Returns

MolangValue

source

source: string

Defined in: compiler.ts:76

The source text the expression was compiled from.

Diagnostic

Defined in: diagnostics.ts:9

A problem found while parsing or binding an expression. The engine raises content errors for these and still evaluates the expression to 0.0; this package mirrors that and reports the problem here instead of throwing.

Properties

code

code: DiagnosticCode

Defined in: diagnostics.ts:10

message

message: string

Defined in: diagnostics.ts:11

EntityContext

Defined in: scope.ts:27

Entity state the entity queries read. Implement the members your entities can answer.

Properties

variables?

optional variables?: Map<string, MolangValue>

Defined in: scope.ts:50

Read-write variable.* storage on the entity; not persisted.

Methods

angerLevel()?

optional angerLevel(): number

Defined in: scope.ts:29

The warden's anger level, [0, n).

Returns

number

equipmentCount()?

optional equipmentCount(): number

Defined in: scope.ts:31

Armor pieces equipped, 0 to 5, hands excluded.

Returns

number

hadComponentGroup()?

optional hadComponentGroup(name): boolean

Defined in: scope.ts:33

Whether the entity was loaded from data saved with the named component group.

Parameters

name

string

Returns

boolean

hasAnyFamily()?

optional hasAnyFamily(families): boolean

Defined in: scope.ts:35

Whether the entity belongs to any of the given type families.

Parameters

families

readonly string[]

Returns

boolean

headIsInWater()?

optional headIsInWater(): boolean

Defined in: scope.ts:37

Whether the entity's head is in water.

Returns

boolean

isBaby()?

optional isBaby(): boolean

Defined in: scope.ts:38

Returns

boolean

isOnGround()?

optional isOnGround(): boolean

Defined in: scope.ts:39

Returns

boolean

isUsingItem()?

optional isUsingItem(): boolean

Defined in: scope.ts:40

Returns

boolean

lastHitByPlayer()?

optional lastHitByPlayer(): boolean

Defined in: scope.ts:42

Whether a player dealt the last hit.

Returns

boolean

playerLevel()?

optional playerLevel(): number

Defined in: scope.ts:44

The player's experience level, or 0 for non-players.

Returns

number

property()?

optional property(name): string | number | undefined

Defined in: scope.ts:46

The value of the named entity property, or undefined when it does not exist.

Parameters

name

string

Returns

string | number | undefined

variant()?

optional variant(): number

Defined in: scope.ts:48

The entity's variant index.

Returns

number

ForEachNode

Defined in: ast.ts:111

for_each(variable, array, expression).

Properties

array

array: ExpressionNode

Defined in: ast.ts:114

body

body: ExpressionNode

Defined in: ast.ts:115

kind

kind: "for_each"

Defined in: ast.ts:112

variable

variable: ReferenceNode

Defined in: ast.ts:113

IndexNode

Defined in: ast.ts:70

Array access target[index].

Properties

index

index: ExpressionNode

Defined in: ast.ts:73

kind

kind: "index"

Defined in: ast.ts:71

target

target: ExpressionNode

Defined in: ast.ts:72

ItemContext

Defined in: scope.ts:62

Item stack state for the durability and tag queries.

Methods

maxDurability()?

optional maxDurability(): number

Defined in: scope.ts:63

Returns

number

remainingDurability()?

optional remainingDurability(): number

Defined in: scope.ts:64

Returns

number

tags()?

optional tags(): readonly string[]

Defined in: scope.ts:66

The item's tags, for query.any_tag and query.all_tags.

Returns

readonly string[]

LoopControlNode

Defined in: ast.ts:93

break and continue inside a loop body. They may appear where an expression is expected, as in (v.x > 5) ? break, and evaluate to 0 outside a loop.

Properties

kind

kind: "break" | "continue"

Defined in: ast.ts:94

LoopNode

Defined in: ast.ts:104

loop(count, expression); the engine caps count at 1024.

Properties

body

body: ExpressionNode

Defined in: ast.ts:107

count

count: ExpressionNode

Defined in: ast.ts:106

kind

kind: "loop"

Defined in: ast.ts:105

MathFunction

Defined in: math.ts:2

A Molang math function: a pure numeric function over already-evaluated arguments.

Properties

evaluate

evaluate: (args) => number

Defined in: math.ts:4

Evaluates the function. Missing arguments read as 0, as Molang errors evaluate to 0.

Parameters

args

readonly number[]

Returns

number

MolangArray

Defined in: scope.ts:18

An actor array, as produced by queries the arrow and for_each constructs consume.

Properties

elements

elements: readonly MolangValue[]

Defined in: scope.ts:20

kind

kind: "array"

Defined in: scope.ts:19

MolangExample

Defined in: examples.ts:12

A Molang expression a pack author could write, with the scopes it is shown to work under.

Properties

cases

readonly cases: readonly MolangExampleCase[]

Defined in: examples.ts:20

description

readonly description: string

Defined in: examples.ts:16

Where an author would put it and what it does.

minEngineVersion?

readonly optional minEngineVersion?: readonly [number, number, number]

Defined in: examples.ts:19

The pack's min_engine_version when the expression depends on one.

source

readonly source: string

Defined in: examples.ts:17

title

readonly title: string

Defined in: examples.ts:14

A short name, used as the heading in the README.

MolangExampleCase

Defined in: examples.ts:4

One evaluation of an example: what the scope answers and the value that comes out.

Properties

expected

readonly expected: MolangValue

Defined in: examples.ts:8

label

readonly label: string

Defined in: examples.ts:6

What is different about this scope, in a few words.

scope

readonly scope: MolangScope

Defined in: examples.ts:7

MolangOptions

Defined in: Molang.ts:19

Options for a Molang engine.

Properties

queries?

optional queries?: QueryRegistry

Defined in: Molang.ts:21

The query registry to bind query.* names against; a fresh vanilla registry by default.

MolangScope

Defined in: scope.ts:95

Everything one evaluation can see. Queries declare which of these members they need; the compiler reports a query bound against a scope that was declared without its context.

Properties

block?

optional block?: BlockContext

Defined in: scope.ts:97

context?

optional context?: ReadonlyMap<string, MolangValue>

Defined in: scope.ts:102

Read-only values the game supplies for the expression, such as context.other.

entity?

optional entity?: EntityContext

Defined in: scope.ts:96

item?

optional item?: ItemContext

Defined in: scope.ts:98

placement?

optional placement?: PlacementContext

Defined in: scope.ts:100

variables?

optional variables?: Map<string, MolangValue>

Defined in: scope.ts:104

variable.* storage when no entity carries it, as for feature-rule engine variables.

world?

optional world?: WorldContext

Defined in: scope.ts:99

MolangScopeRef

Defined in: scope.ts:12

A reference to another evaluation scope, used by the arrow operator and this. The engine's actor references map to this: context.other->query.remaining_durability evaluates its right side against the referenced scope.

Properties

kind

kind: "scope"

Defined in: scope.ts:13

scope

scope: MolangScope

Defined in: scope.ts:14

MolangStruct

Defined in: scope.ts:2

A struct value, implicitly defined by usage such as v.location.x = 1;.

Properties

kind

kind: "struct"

Defined in: scope.ts:3

members

members: Map<string, MolangValue>

Defined in: scope.ts:4

MolangVersionRules

Defined in: version.ts:13

The language rules that change with a pack's min_engine_version.

The engine versions each Molang expression by the manifest of the pack that contains it. Two changes affect parsing: at 1.18.10 the ternary became right-associative, and at 1.18.20 && started binding tighter than || and comparisons tighter than equality. One change affects evaluation: at 1.19.60 division by a dynamically determined negative value stopped dividing by its absolute value.

Properties

andBeforeOr

andBeforeOr: boolean

Defined in: version.ts:17

&& binds tighter than || and comparison tighter than equality from 1.18.20.

divideByNegativeValue

divideByNegativeValue: boolean

Defined in: version.ts:19

Division by a non-constant negative divisor uses the real divisor from 1.19.60.

ternaryRightAssociative

ternaryRightAssociative: boolean

Defined in: version.ts:15

A ? B : C ? D : E groups as A ? B : (C ? D : E) from 1.18.10.

NumberNode

Defined in: ast.ts:2

A numeric literal. Molang numbers are floats; true and false lex to 1 and 0.

Properties

kind

kind: "number"

Defined in: ast.ts:3

value

value: number

Defined in: ast.ts:4

PlacementContext

Defined in: scope.ts:80

Feature placement state for the worldgen queries.

Methods

aboveTopSolid()?

optional aboveTopSolid(x, z): number

Defined in: scope.ts:84

The height of the block above the highest solid block at (x, z).

Parameters

x

number

z

number

Returns

number

hasBiomeTag()?

optional hasBiomeTag(tag, x?, y?, z?): boolean

Defined in: scope.ts:88

Whether the biome at the placement position (or the given one) has the tag.

Parameters

tag

string

x?

number

y?

number

z?

number

Returns

boolean

heightmap()?

optional heightmap(x, z): number

Defined in: scope.ts:82

The world-surface height (Y) at (x, z).

Parameters

x

number

z

number

Returns

number

noise()?

optional noise(x, z): number

Defined in: scope.ts:86

A Perlin noise value near [-1, 1] for (x, z).

Parameters

x

number

z

number

Returns

number

ProgramNode

Defined in: ast.ts:143

A parsed Molang expression. A simple expression has one statement and no ; and returns its value; a complex expression runs its statements and returns 0 unless a return runs.

Properties

complex

complex: boolean

Defined in: ast.ts:145

kind

kind: "program"

Defined in: ast.ts:144

statements

statements: readonly StatementNode[]

Defined in: ast.ts:146

QueryDefinition

Defined in: queries.ts:7

A registered query: the context it needs and its implementation.

Properties

context

context: QueryContextKind

Defined in: queries.ts:9

Which part of the scope the query reads; loaders can validate fields against it.

evaluate

evaluate: (scope, args) => MolangValue

Defined in: queries.ts:11

Evaluates the query over already-evaluated arguments.

Parameters

ReferenceNode

Defined in: ast.ts:18

A dotted reference such as query.is_baby, variable.a.b or math.pi. domain is the normalized first segment (aliases q, v, t and c are expanded) and path the remaining segments.

Properties

domain

domain: "query" | "math" | "variable" | "temp" | "context" | "geometry" | "material" | "texture" | "array"

Defined in: ast.ts:20

kind

kind: "reference"

Defined in: ast.ts:19

path

path: readonly string[]

Defined in: ast.ts:21

ReturnNode

Defined in: ast.ts:84

return <expression>; ends the whole expression with the value.

Properties

kind

kind: "return"

Defined in: ast.ts:85

value

value: ExpressionNode

Defined in: ast.ts:86

StringNode

Defined in: ast.ts:8

A single-quoted string literal with its case preserved.

Properties

kind

kind: "string"

Defined in: ast.ts:9

value

value: string

Defined in: ast.ts:10

TernaryNode

Defined in: ast.ts:55

A ? B : C, or the binary conditional A ? B when otherwise is undefined.

Properties

condition

condition: ExpressionNode

Defined in: ast.ts:57

kind

kind: "ternary"

Defined in: ast.ts:56

otherwise?

optional otherwise?: ExpressionNode

Defined in: ast.ts:59

then

then: ExpressionNode

Defined in: ast.ts:58

ThisNode

Defined in: ast.ts:25

this, the value the expression ultimately writes to.

Properties

kind

kind: "this"

Defined in: ast.ts:26

Token

Defined in: lexer.ts:11

A lexed token. value is lowercased except for string contents, which keep their case.

Properties

kind

kind: TokenKind

Defined in: lexer.ts:12

start

start: number

Defined in: lexer.ts:15

Offset of the token's first character in the source text.

value

value: string

Defined in: lexer.ts:13

UnaryNode

Defined in: ast.ts:37

A unary operation, !a or -a.

Properties

kind

kind: "unary"

Defined in: ast.ts:38

operand

operand: ExpressionNode

Defined in: ast.ts:40

operator

operator: "!" | "-"

Defined in: ast.ts:39

WorldContext

Defined in: scope.ts:70

Level state the world queries read.

Methods

day()?

optional day(): number

Defined in: scope.ts:73

Returns

number

moonBrightness()?

optional moonBrightness(): number

Defined in: scope.ts:75

Returns

number

moonPhase()?

optional moonPhase(): number

Defined in: scope.ts:74

Returns

number

timeOfDay()?

optional timeOfDay(): number

Defined in: scope.ts:72

Time of day in [0, 1): midnight 0.0, sunrise 0.25, noon 0.5, sunset 0.75.

Returns

number

timeStamp()?

optional timeStamp(): number

Defined in: scope.ts:76

Returns

number

Type Aliases

BinaryOperator

BinaryOperator = "+" | "-" | "*" | "/" | "<" | "<=" | ">" | ">=" | "==" | "!=" | "&&" | "||" | "??"

Defined in: ast.ts:44

The binary operators of the language, including ??.

DiagnosticCode

DiagnosticCode = "syntax-error" | "unknown-query" | "unknown-math-function" | "client-only-resource"

Defined in: diagnostics.ts:2

What a diagnostic reports.

EngineVersion

EngineVersion = readonly [number, number, number]

Defined in: version.ts:2

A pack min_engine_version triple, as found in a manifest header.

ExpressionNode

ExpressionNode = NumberNode | StringNode | ReferenceNode | ThisNode | CallNode | UnaryNode | BinaryNode | TernaryNode | ArrowNode | IndexNode | AssignNode | BlockNode | LoopNode | ForEachNode | LoopControlNode

Defined in: ast.ts:119

Any expression form.

Keyword

Keyword = typeof KEYWORDS[number]

Defined in: lexer.ts:5

One of KEYWORDS.

MathFunctionName

MathFunctionName = keyof typeof MATH_FUNCTIONS

Defined in: math.ts:168

The name of a known math.* function.

MolangValue

MolangValue = number | string | MolangStruct | MolangScopeRef | MolangArray

Defined in: scope.ts:24

A runtime Molang value. Numbers carry booleans as 0.0 and 1.0.

QueryContextKind

QueryContextKind = "entity" | "block" | "item" | "world" | "placement" | "tags" | "pure"

Defined in: queries.ts:4

The scope member a query reads. tags resolves to the item when present, else the block.

StatementNode

StatementNode = ExpressionNode | ReturnNode

Defined in: ast.ts:137

A statement in a complex expression.

TokenKind

TokenKind = "number" | "string" | "identifier" | "keyword" | "operator"

Defined in: lexer.ts:8

The lexical category of a token.

VanillaQueryName

VanillaQueryName = keyof typeof VANILLA_QUERIES

Defined in: queries.ts:134

The name of a registered vanilla server-side query.

Variables

KEYWORDS

const KEYWORDS: readonly ["return", "loop", "for_each", "break", "continue", "this", "true", "false"]

Defined in: lexer.ts:2

Keywords the parser treats specially. Everything else that looks like a word is an identifier.

LATEST_RULES

const LATEST_RULES: MolangVersionRules

Defined in: version.ts:35

The rules the latest engine applies; used when a caller gives no version.

MATH_FUNCTIONS

const MATH_FUNCTIONS: object

Defined in: math.ts:95

The 61 documented math.* functions with Bedrock's semantics: trigonometry in degrees, sign(0) is -1, mod keeps the dividend's sign like C fmod, die_roll sums num random floats, and the 30 easing functions map (start, end, t) along the Penner curves.

Type Declaration

abs

readonly abs: MathFunction

acos

readonly acos: MathFunction

asin

readonly asin: MathFunction

atan

readonly atan: MathFunction

atan2

readonly atan2: MathFunction

ceil

readonly ceil: MathFunction

clamp

readonly clamp: MathFunction

copy_sign

readonly copy_sign: MathFunction

cos

readonly cos: MathFunction

die_roll

readonly die_roll: MathFunction

die_roll_integer

readonly die_roll_integer: MathFunction

ease_in_back

readonly ease_in_back: MathFunction

ease_in_bounce

readonly ease_in_bounce: MathFunction

ease_in_circ

readonly ease_in_circ: MathFunction

ease_in_cubic

readonly ease_in_cubic: MathFunction

ease_in_elastic

readonly ease_in_elastic: MathFunction

ease_in_expo

readonly ease_in_expo: MathFunction

ease_in_out_back

readonly ease_in_out_back: MathFunction

ease_in_out_bounce

readonly ease_in_out_bounce: MathFunction

ease_in_out_circ

readonly ease_in_out_circ: MathFunction

ease_in_out_cubic

readonly ease_in_out_cubic: MathFunction

ease_in_out_elastic

readonly ease_in_out_elastic: MathFunction

ease_in_out_expo

readonly ease_in_out_expo: MathFunction

ease_in_out_quad

readonly ease_in_out_quad: MathFunction

ease_in_out_quart

readonly ease_in_out_quart: MathFunction

ease_in_out_quint

readonly ease_in_out_quint: MathFunction

ease_in_out_sine

readonly ease_in_out_sine: MathFunction

ease_in_quad

readonly ease_in_quad: MathFunction

ease_in_quart

readonly ease_in_quart: MathFunction

ease_in_quint

readonly ease_in_quint: MathFunction

ease_in_sine

readonly ease_in_sine: MathFunction

ease_out_back

readonly ease_out_back: MathFunction

ease_out_bounce

readonly ease_out_bounce: MathFunction

ease_out_circ

readonly ease_out_circ: MathFunction

ease_out_cubic

readonly ease_out_cubic: MathFunction

ease_out_elastic

readonly ease_out_elastic: MathFunction

ease_out_expo

readonly ease_out_expo: MathFunction

ease_out_quad

readonly ease_out_quad: MathFunction

ease_out_quart

readonly ease_out_quart: MathFunction

ease_out_quint

readonly ease_out_quint: MathFunction

ease_out_sine

readonly ease_out_sine: MathFunction

exp

readonly exp: MathFunction

floor

readonly floor: MathFunction

hermite_blend

readonly hermite_blend: MathFunction

inverse_lerp

readonly inverse_lerp: MathFunction

lerp

readonly lerp: MathFunction

lerprotate

readonly lerprotate: MathFunction

ln

readonly ln: MathFunction

max

readonly max: MathFunction

min

readonly min: MathFunction

min_angle

readonly min_angle: MathFunction

mod

readonly mod: MathFunction

pi

readonly pi: MathFunction

pow

readonly pow: MathFunction

random

readonly random: MathFunction

random_integer

readonly random_integer: MathFunction

round

readonly round: MathFunction

sign

readonly sign: MathFunction

sin

readonly sin: MathFunction

sqrt

readonly sqrt: MathFunction

trunc

readonly trunc: MathFunction

MOLANG_EXAMPLES

const MOLANG_EXAMPLES: readonly MolangExample[]

Defined in: examples.ts:32

Expressions that compile and evaluate on this engine, each with the values it produces.

The README shows exactly these sources, and examples.test.ts fails when the two differ or when an example stops producing its values, so none of them can quietly rot. A tool that wants real Molang to try - an editor, a playground, a documentation page - can take them from here.

VANILLA_QUERIES

const VANILLA_QUERIES: object

Defined in: queries.ts:26

The 21 queries the vanilla behavior pack uses server-side, keyed without the query. prefix. Each declares the scope context it reads.

Type Declaration

above_top_solid

readonly above_top_solid: object

above_top_solid.context

readonly context: "placement" = 'placement'

above_top_solid.evaluate

readonly evaluate: (scope, args) => number

Parameters

scope

MolangScope

args

readonly MolangValue[]

Returns

number

all_tags

readonly all_tags: object

all_tags.context

readonly context: "tags" = 'tags'

all_tags.evaluate

readonly evaluate: (scope, args) => 0 | 1

Parameters

scope

MolangScope

args

readonly MolangValue[]

Returns

0 | 1

anger_level

readonly anger_level: object

anger_level.context

readonly context: "entity" = 'entity'

anger_level.evaluate

readonly evaluate: (scope) => number

Parameters

scope

MolangScope

Returns

number

any_tag

readonly any_tag: object

any_tag.context

readonly context: "tags" = 'tags'

any_tag.evaluate

readonly evaluate: (scope, args) => 0 | 1

Parameters

scope

MolangScope

args

readonly MolangValue[]

Returns

0 | 1

block_state

readonly block_state: object

block_state.context

readonly context: "block" = 'block'

block_state.evaluate

readonly evaluate: (scope, args) => string | number

Parameters

scope

MolangScope

args

readonly MolangValue[]

Returns

string | number

equipment_count

readonly equipment_count: object

equipment_count.context

readonly context: "entity" = 'entity'

equipment_count.evaluate

readonly evaluate: (scope) => number

Parameters

scope

MolangScope

Returns

number

had_component_group

readonly had_component_group: object

had_component_group.context

readonly context: "entity" = 'entity'

had_component_group.evaluate

readonly evaluate: (scope, args) => 0 | 1

Parameters

scope

MolangScope

args

readonly MolangValue[]

Returns

0 | 1

has_any_family

readonly has_any_family: object

has_any_family.context

readonly context: "entity" = 'entity'

has_any_family.evaluate

readonly evaluate: (scope, args) => 0 | 1

Parameters

scope

MolangScope

args

readonly MolangValue[]

Returns

0 | 1

has_biome_tag

readonly has_biome_tag: object

has_biome_tag.context

readonly context: "placement" = 'placement'

has_biome_tag.evaluate

readonly evaluate: (scope, args) => 0 | 1

Parameters

scope

MolangScope

args

readonly MolangValue[]

Returns

0 | 1

head_is_in_water

readonly head_is_in_water: object

head_is_in_water.context

readonly context: "entity" = 'entity'

head_is_in_water.evaluate

readonly evaluate: (scope) => 0 | 1

Parameters

scope

MolangScope

Returns

0 | 1

heightmap

readonly heightmap: object

heightmap.context

readonly context: "placement" = 'placement'

heightmap.evaluate

readonly evaluate: (scope, args) => number

Parameters

scope

MolangScope

args

readonly MolangValue[]

Returns

number

is_baby

readonly is_baby: object

is_baby.context

readonly context: "entity" = 'entity'

is_baby.evaluate

readonly evaluate: (scope) => 0 | 1

Parameters

scope

MolangScope

Returns

0 | 1

is_on_ground

readonly is_on_ground: object

is_on_ground.context

readonly context: "entity" = 'entity'

is_on_ground.evaluate

readonly evaluate: (scope) => 0 | 1

Parameters

scope

MolangScope

Returns

0 | 1

is_using_item

readonly is_using_item: object

is_using_item.context

readonly context: "entity" = 'entity'

is_using_item.evaluate

readonly evaluate: (scope) => 0 | 1

Parameters

scope

MolangScope

Returns

0 | 1

last_hit_by_player

readonly last_hit_by_player: object

last_hit_by_player.context

readonly context: "entity" = 'entity'

last_hit_by_player.evaluate

readonly evaluate: (scope) => 0 | 1

Parameters

scope

MolangScope

Returns

0 | 1

max_durability

readonly max_durability: object

max_durability.context

readonly context: "item" = 'item'

max_durability.evaluate

readonly evaluate: (scope) => number

Parameters

scope

MolangScope

Returns

number

noise

readonly noise: object

noise.context

readonly context: "placement" = 'placement'

noise.evaluate

readonly evaluate: (scope, args) => number

Parameters

scope

MolangScope

args

readonly MolangValue[]

Returns

number

player_level

readonly player_level: object

player_level.context

readonly context: "entity" = 'entity'

player_level.evaluate

readonly evaluate: (scope) => number

Parameters

scope

MolangScope

Returns

number

property

readonly property: object

property.context

readonly context: "entity" = 'entity'

property.evaluate

readonly evaluate: (scope, args) => string | number

Parameters

scope

MolangScope

args

readonly MolangValue[]

Returns

string | number

remaining_durability

readonly remaining_durability: object

remaining_durability.context

readonly context: "item" = 'item'

remaining_durability.evaluate

readonly evaluate: (scope) => number

Parameters

scope

MolangScope

Returns

number

variant

readonly variant: object

variant.context

readonly context: "entity" = 'entity'

variant.evaluate

readonly evaluate: (scope) => number

Parameters

scope

MolangScope

Returns

number

Functions

compileProgram()

compileProgram(source, program, rules, queries): CompiledMolang

Defined in: compiler.ts:86

Compiles a parsed program into a closure over a scope.

Parameters

source

string

program

ProgramNode

rules

MolangVersionRules

queries

QueryRegistry

Returns

CompiledMolang

parse()

parse(source, rules): ProgramNode

Defined in: parser.ts:283

Parses Molang source text into an AST under the given versioned rules.

Parameters

source

string

rules

MolangVersionRules

Returns

ProgramNode

Throws

When the text is not a valid Molang expression.

rulesForEngineVersion()

rulesForEngineVersion(version): MolangVersionRules

Defined in: version.ts:26

Derives the versioned language rules from a pack's min_engine_version.

Parameters

version

EngineVersion

Returns

MolangVersionRules

tokenize()

tokenize(source): Token[]

Defined in: lexer.ts:43

Splits Molang source text into tokens. Molang is case-insensitive except inside strings, so identifiers and keywords are lowercased here and string contents are preserved.

Parameters

source

string

Returns

Token[]

Throws

When the text contains an unexpected character or an unterminated string.

Namespaces

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Namespaces

Structure

Classes

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Types

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Logger

Types

Classes

@jsprismarine/molang ​

Examples ​

A chance that depends on age ​

A value kept in range ​

A spawn condition ​

A string property ​

Worn-out tools ​

Interpolating between two numbers ​

A reward that grows with level ​

A terrain condition ​

A complex expression with a loop ​

Stopping a loop early ​

Classes ​

Interfaces ​

ArrowNode ​

Properties ​

kind ​

left ​

right ​

AssignNode ​

Properties ​

kind ​

target ​

value ​

BinaryNode ​

Properties ​

kind ​

left ​

@jsprismarine/molang

Examples

A chance that depends on age

A value kept in range

A spawn condition

A string property

Worn-out tools

Interpolating between two numbers

A reward that grows with level

A terrain condition

A complex expression with a loop

Stopping a loop early

Classes

Interfaces

ArrowNode

Properties

kind

left

right

AssignNode

Properties

kind

target

value

BinaryNode

Properties

kind

left

operator

right

BlockContext

Methods

blockState()?

Parameters

name

Returns

tags()?

Returns

BlockNode

Properties

kind

statements

CallNode

Properties

args

callee

kind

CompileOptions

Properties

minEngineVersion?

CompiledMolang

Properties

ast?

diagnostics