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https://github.com/lys-lang/node-ebnf
Create AST PEG Parsers from formal grammars in JavaScript
https://github.com/lys-lang/node-ebnf
Last synced: 3 days ago
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Create AST PEG Parsers from formal grammars in JavaScript
- Host: GitHub
- URL: https://github.com/lys-lang/node-ebnf
- Owner: lys-lang
- License: mit
- Created: 2016-10-02T18:05:22.000Z (about 8 years ago)
- Default Branch: master
- Last Pushed: 2023-06-08T22:19:59.000Z (over 1 year ago)
- Last Synced: 2024-11-02T17:06:17.245Z (6 days ago)
- Language: TypeScript
- Homepage: https://menduz.com/ebnf-highlighter/
- Size: 471 KB
- Stars: 104
- Watchers: 9
- Forks: 9
- Open Issues: 19
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
- awesome-javascript - ebnf
- awesome-javascript - ebnf
README
[](https://coveralls.io/github/menduz/node-ebnf?branch=master)
[](https://travis-ci.org/lys-lang/node-ebnf)
# What is this?
It parses a formal grammar and returns a parser instance. That parser returns ASTs based on your grammar. [**SEE IT IN ACTION HERE**](http://menduz.com/ebnf-highlighter/) [GitHub source](https://github.com/menduz/ebnf-highlighter)
# Install
`npm i --save ebnf` (It's compatible with WebPack, and Browserify)
# Usage
By the moment we only accept two grammars. [BNF](https://en.wikipedia.org/wiki/Backus%E2%80%93Naur_Form) and [W3C EBNF](http://www.w3.org/TR/xquery/#EBNFNotation) (compatible with [Railroad Diagram Generator](http://www.bottlecaps.de/rr/ui))
## Create a parser
```typescript
import { Grammars } from 'ebnf';
let bnfParser = new Grammars.BNF.Parser(bnfGrammar);
let w3cParser = new Grammars.W3C.Parser(railRoadGeneratorGrammar);
```
[**Check out the test folder for more examples**](https://github.com/menduz/node-ebnf/tree/master/test)
## BNF Equation example
In this example we use plain BNF to create a simple integer formula parser
Grammar:
```ebnf
::= |
::= "(" ")" | "(" ")" |
::=
::= | |
::= "+" | "-" | "*" | "/" | "^"
::= |
::= "-"
::= "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9"
::= "0" |
::= | ""
::= " " | | " " |
```
```typescript
import { Grammars } from 'ebnf';
let parser = new Grammars.BNF.Parser(grammar);
parser.getAST('-122 + 2');
/* -122 + 2 Equation
-122 + 2 BinaryOperation
-122 Term
-122 Number
+ Operator
2 Term
2 Number
*/
parser.getAST( '(2 + (2 * -123)) * 5332');
/* (2 + (2 * -123)) * 5332 Equation
(2 + (2 * -123)) * 5332 BinaryOperation
(2 + (2 * -123)) Term
2 + (2 * -123) Equation
2 + (2 * -123) BinaryOperation
2 Term
2 Number
+ Operator
(2 * -123) Term
2 * -123 Equation
2 * -123 BinaryOperation
2 Term
2 Number
* Operator
-123 Term
-123 Number
* Operator
5332 Term
5332 Number
*/
```
## JSON example
```wbnf
/* https://www.ietf.org/rfc/rfc4627.txt */
value ::= false | null | true | object | array | number | string
BEGIN_ARRAY ::= WS* #x5B WS* /* [ left square bracket */
BEGIN_OBJECT ::= WS* #x7B WS* /* { left curly bracket */
END_ARRAY ::= WS* #x5D WS* /* ] right square bracket */
END_OBJECT ::= WS* #x7D WS* /* } right curly bracket */
NAME_SEPARATOR ::= WS* #x3A WS* /* : colon */
VALUE_SEPARATOR ::= WS* #x2C WS* /* , comma */
WS ::= [#x20#x09#x0A#x0D]+ /* Space | Tab | \n | \r */
false ::= "false"
null ::= "null"
true ::= "true"
object ::= BEGIN_OBJECT (member (VALUE_SEPARATOR member)*)? END_OBJECT
member ::= string NAME_SEPARATOR value
array ::= BEGIN_ARRAY (value (VALUE_SEPARATOR value)*)? END_ARRAY
number ::= "-"? ("0" | [1-9] [0-9]*) ("." [0-9]+)? (("e" | "E") ( "-" | "+" )? ("0" | [1-9] [0-9]*))?
/* STRINGS */
string ::= '"' (([#x20-#x21] | [#x23-#x5B] | [#x5D-#xFFFF]) | #x5C (#x22 | #x5C | #x2F | #x62 | #x66 | #x6E | #x72 | #x74 | #x75 HEXDIG HEXDIG HEXDIG HEXDIG))* '"'
HEXDIG ::= [a-fA-F0-9]
```
```typescript
import { Grammars } from 'ebnf';
let parser = new Grammars.W3C.Parser(grammar);
parser.getAST( '{"a":false,"b":"asd\\n asd ","list":[1,2,3,true]}');
/* {"a":false,"b":"asd\n asd ","list":[1,2,3,true]} value
{"a":false,"b":"asd\n asd ","list":[1,2,3,true]} object
"a":false member
"a" string
false value
false false
"b":"asd\n asd " member
"b" string
"asd\n asd " value
"asd\n asd " string
"list":[1,2,3,true] member
"list" string
[1,2,3,true] value
[1,2,3,true] array
1 value
1 number
2 value
2 number
3 value
3 number
true value
true true
*/
```
## AST
Every ast node has the following interface
```typescript
interface IToken {
type: string; // Rule name
text: string; // Inner text
children: IToken[]; // Children nodes
start: number; // Start position of the input string
end: number; // End position
errors: TokenError[]; // List of Errors
}
```
## Conventions
We try to keep this tool as much unopinionated and free of conventions as possible. However, we have some conventions:
- All `UPPER_AND_SNAKE_CASE` rules are not emmited on the AST. This option can be deactivated setting the flag `keepUpperRules: true`.