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Original source (sap.github.io)
Tags: javascript dsl
Clipped on: 2016-03-11

Parser

Grammar:

x
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        { ALT: function () { return Number($.CONSUME(NumberLiteral).image) }},
 
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(function jsonExample() {
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  // ----------------- Lexer -----------------
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  var extendToken = chevrotain.extendToken;
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  var Lexer = chevrotain.Lexer;
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  // In ES6, custom inheritance implementation
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  // (such as the one above) can be replaced
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  // with a more simple: "class X extends Y"...
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  var True = extendToken("True", /true/);
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  var False = extendToken("False", /false/);
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  var Null = extendToken("Null", /null/);
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  var LCurly = extendToken("LCurly", /{/);
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  var RCurly = extendToken("RCurly", /}/);
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  var LSquare = extendToken("LSquare", /\[/);
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  var RSquare = extendToken("RSquare", /]/);
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  var Comma = extendToken("Comma", /,/);
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  var Colon = extendToken("Colon", /:/);
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  var StringLiteral = extendToken("StringLiteral",
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    /"(:?[^\\"\n\r]+|\\(:?[bfnrtv"\\/]|u[0-9a-fA-F]{4}))*"/);
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  var NumberLiteral = extendToken("NumberLiteral",
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    /-?(0|[1-9]\d*)(\.\d+)?([eE][+-]?\d+)?/);
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  var WhiteSpace = extendToken("WhiteSpace", /\s+/);
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  WhiteSpace.GROUP = Lexer.SKIPPED;
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  var jsonTokens = [WhiteSpace, NumberLiteral, StringLiteral, RCurly, LCurly,
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    LSquare, RSquare, Comma, Colon, True, False, Null];
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  var ChevJsonLexer = new Lexer(jsonTokens, true);
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  // ----------------- parser -----------------
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  var ChevrotainParser = chevrotain.Parser;
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  function ChevrotainJsonParser(input) {
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    ChevrotainParser.call(this, input, jsonTokens);
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    var $ = this;
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    this.json = this.RULE("json", function () {
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      // @formatter:off
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      return $.OR([
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        { ALT: function () { return $.SUBRULE($.object) }},
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        { ALT: function () { return $.SUBRULE($.array) }}
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      ]);
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      // @formatter:on
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    });
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    this.object = this.RULE("object", function () {
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      // use debugger statements to add breakpoints
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      // (if your browser supports debugging evaluated code)

Input

Sample:

1
301
6
 
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{
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    "firstName": "John",
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    "lastName": "Smith",
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    "isAlive": true,
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    "age": 25
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}

Syntax Diagrams

json

object array

object

LCurly objectItem objectItem Comma objectItem objectItem RCurly

objectItem

StringLiteral Colon value

array

LSquare value value Comma value value RSquare

value

StringLiteral NumberLiteral object array True False Null

Output

6
 
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{
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    "firstName": "John",
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    "lastName": "Smith",
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    "isAlive": true,
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    "age": 25
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}