@scaffdog/engine

A module of scaffdog template engine.

Install

Install via npm:

``bash
$ npm install @scaffdog/engine
`

Usage

The following code is a basic example:

`typescript
import { render, createContext } from '@scaffdog/engine';

const context = createContext({
variables: new Map([['name', 'scaffdog']]),
helpers: new Map([['greet', (_, name: string) => Hi ${name}!]]),
});

const output = render(OUTPUT: {{ name | greet }}, context);
// --> "OUTPUT: Hi scaffdog!"
`

$3

You can change the tag delimiter with context.tags:

`typescript
import { render, createContext } from '@scaffdog/engine';

const context = createContext({
tags: ['<%=', '=%>'],
});

render(<%= "custom tag" =%>, context);
`

Language Specification

scaffdog uses the template engine inpired by ECMAScript and Go text/template.

`ebnf
SourceCharacter ::= #x0000-#x10FFFF
WhiteSpace ::= "" | "" | "" | " "

Comment ::= "/" CommentChars? "/"
CommentChars ::= NotAsteriskChar CommentChars? | "*" PostAsteriskCommentChars?
PostAsteriskCommentChars ::= NotForwardSlashOrAsteriskChar CommentChars? | "*" PostAsteriskCommentChars?
NotAsteriskChar ::= [^*]
NotForwardSlashOrAsteriskChar ::= [^/*]
NonZeroDigit ::= "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9"
Digit ::= "0" | NonZeroDigit

NullLiteral ::= "null"
UndefinedLiteral ::= "undefined"
BooleanLiteral ::= "true" | "false"
NumericLiteral ::= DecimalLiteral | BinaryIntegerLiteral | OctalIntegerLiteral | HexIntegerLiteral
DecimalLiteral ::= DecimalIntegerLiteral "." DecimalDigits? ExponentPart?
| "." DecimalDigits ExponentPart?
| DecimalIntegerLiteral ExponentPart?
DecimalIntegerLiteral ::= "0"
| NonZeroDigit
| NonZeroDigit DecimalDigits
DecimalDigits ::= Digit | DecimalDigits Digit
ExponentPart ::= ExponentIndicator SignedInteger
ExponentIndicator ::= "e" | "E"
SignedInteger ::= DecimalDigits | "+" DecimalDigits | "-" DecimalDigits
BinaryIntegerLiteral ::= "0b" BinaryDigits | "0B" BinaryDigits
BinaryDigits ::= BinaryDigit | BinaryDigits BinaryDigit
BinaryDigit ::= "0" | "1"
OctalIntegerLiteral ::= "0o" OctalDigits | "0O" OctalDigits
OctalDigits ::= OctalDigit | OctalDigits OctalDigit
OctalDigit ::= "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7"
HexIntegerLiteral ::= "0x" HexDigits | "0X" HexDigits
HexDigits ::= HexDigit | HexDigits HexDigit
HexDigit ::= "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9" | "a" | "b" | "c" | "d" | "e" | "f" | "A" | "B" | "C" | "D" | "E" | "F"
StringLiteral ::= DoubleStringLiteral | SingleStringLiteral
DoubleStringLiteral ::= '"' DoubleStringChars '"'
DoubleStringChars ::= DoubleStringChar | DoubleStringChar DoubleStringChars
DoubleStringChar ::= EscapeChar | SourceCharacter - '"'
SingleStringLiteral ::= '"' SingleStringChars '"'
SingleStringChars ::= SingleStringChar | SingleStringChar SingleStringChars
SingleStringChar ::= EscapeChar | SourceCharacter - "'"
EscapeChar ::= '\"' | "\'"

Literal ::= NullLiteral | UndefinedLiteral | BooleanLiteral | NumericLiteral | StringLiteral

ReservedWord ::= "null" | "true" | "false" | "undefined" | "if" | "else" | "break" | "continue" | "end" | "for"

/ Expressions /
Identifier ::= IdentifierName - ReservedWord
IdentifierName ::= IdentifierStart | IdentifierName IdentifierPart
IdentifierStart ::= "$" | "_" | UnicodeIDStart
IdentifierPart ::= "$" | "_" | UnicodeIDContinue
UnicodeIDStart ::= / any Unicode code point with the Unicode property “ID_Start” /
UnicodeIDContinue ::= / any Unicode code point with the Unicode property “ID_Continue” /

PrimaryExpression ::= Identifier
| Literal
| ParenthesizedExpression

StaticMemberAccessor ::= Identifier | NumericLiteral
MemberExpression ::= PrimaryExpression
| MemberExpression "[" Expression "]"
| MemberExpression "." StaticMemberAccessor

CallExpression ::= MemberExpression Arguments
| CallExpression Arguments
| CallExpression "[" Expression "]"
| CallExpression "." StaticMemberAccessor

LeftHandSideExpression ::= CallExpression | MemberExpression
UpdateExpression ::= LeftHandSideExpression
| LeftHandSideExpression "++"
| LeftHandSideExpression "--"
| "++" LeftHandSideExpression
| "--" LeftHandSideExpression
UnaryExpression ::= UpdateExpression |
| "+" UnaryExpression
| "-" UnaryExpression
| "~" UnaryExpression
| "!" UnaryExpression

MultiplicativeOperator ::= [* / %]
MultiplicativeExpression ::= UnaryExpression
| MultiplicativeExpression MultiplicativeOperator UnaryExpression
AdditiveExpression ::= MultiplicativeExpression
| AdditiveExpression "+" MultiplicativeExpression
| AdditiveExpression "-" MultiplicativeExpression
RelationalExpression::= AdditiveExpression
| RelationalExpression "<" AdditiveExpression
| RelationalExpression ">" AdditiveExpression
| RelationalExpression "<=" AdditiveExpression
| RelationalExpression ">=" AdditiveExpression

EqualityExpression ::= RelationalExpression
| EqualityExpression "==" RelationalExpression
| EqualityExpression "!=" RelationalExpression

LogicalANDExpression ::= LogicalANDExpression "&&" EqualityExpression
LogicalORExpression ::= LogicalORExpression "||" LogicalANDExpression

ConditionalExpression ::= LogicalORExpression
| ConditionalExpression "?" ConditionalExpression ":" ConditionalExpression

ArgumentItem ::= ConditionalExpression | CallExpression
ArgumentList ::= ArgumentItem | ArgumentList "," ArgumentItem
Arguments ::= "(" ")" | "(" ArgumentList ")"

ParenthesizedExpression ::= "(" Expression ")"

PipeArgument ::= UnaryExpression
PipeArgumentList ::= PipeArgument | PipeArgumentList WhiteSpace PipeArgument
PipeHead ::= ConditionalExpression PipeArgumentList?
| LeftHandSideExpression PipeArgumentList?
PipeBody ::= MemberExpression PipeArgumentList?
PipeExpression ::= PipeHead
| PipeHead "|" PipeBody
| PipeExpression "|" PipeBody

Expression ::= PipeExpression

/ Statements /
TagOpen ::= "{{" | "{{-"
TagClose ::= "}}" | "}}-"

ExpressionStatement ::= Expression
VariableStatement ::= Identifier ":=" Expression
EndStatement ::= "end"
ContinueStatement ::= "continue"
BreakStatement ::= "break"
ForBinding ::= Identifier | Identifier "," Identifier
ForStatement ::= "for" ForBinding "in" Expression TagClose Template TagOpen EndStatement
IfStatement ::= "if" Expression TagClose Template TagOpen EndStatement
| "if" Expression TagClose Template TagOpen "else" TagClose Template TagOpen EndStatement
| "if" Expression TagClose Template TagOpen "else" IfStatement
Statement ::= VariableStatement
| IfStatement
| ForStatement
| ContinueStatement
| BreakStatement
| ExpressionStatement

/ Templates /
TagTemplate ::= TagOpen Statement TagClose

RawTemplateChar ::= SourceCharacter - TagOpen
RawTemplate ::= RawTemplateChar RawTemplate?

TemplateElement ::= TagTemplate | RawTemplate
Template ::= TemplateElement | Template TemplateElement

Program ::= Template?
``