⚡ Quick Guide: Online Version » PEG.js – Parser Generator for JavaScript

1
Write your PEG.js grammar

// Simple Arithmetics Grammar
// ==========================
//
// Accepts expressions like "2 * (3 + 4)" and computes their value.

Expression
  = head:Term tail:(_ ("+" / "-") _ Term)* {
      return tail.reduce(function(result, element) {
        if (element[1] === "+") { return result + element[3]; }
        if (element[1] === "-") { return result - element[3]; }
      }, head);
    }

Term
  = head:Factor tail:(_ ("*" / "/") _ Factor)* {
      return tail.reduce(function(result, element) {
        if (element[1] === "*") { return result * element[3]; }
        if (element[1] === "/") { return result / element[3]; }
      }, head);
    }

Factor
  = "(" _ expr:Expression _ ")" { return expr; }
  / Integer

Integer "integer"
  = _ [0-9]+ { return parseInt(text(), 10); }

_ "whitespace"
  = [ \t\n\r]*

2
Test the generated parser with some input

2 * (3 + 4)

Parser not available.

Output

Output not available.

3
Download the parser code

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1 Write your PEG.js grammar

2 Test the generated parser with some input

Output

3 Download the parser code

1
Write your PEG.js grammar

2
Test the generated parser with some input

3
Download the parser code