CODEWITHSUNDEEP
javascriptbnfpegpegjs
Chris
Chris

Reputation: 514

Parsing and validating conditional IF in PEG parser

Trying to parse a single line conditional where code tries to test the left hand is equal to the right hand.

{
  user = {id: 'abc123'}
  function_name() {...}
}

if (user.id === 'abc123...') { function_name() }

I've so far looked at these posts PEG-php parsing if statement and How to describe conditional statement (if-then-else) using PEG

PEG syntax is very alien to me, and I'm sure if it's even the right methodology for my needs. Might be overkill.

Currently using peg.js/peggy.js

Upvotes: 0

Views: 465

Answers (1)

Bob
Bob

Reputation: 14664

Your question is very vague, I will try to give you a starting point,

this is a grammar that would consume your example intput.

Code = (Condition / Curly / Statement)+

Curly = '{' code: Code+ '}' { return {nested: code}}

Statement = $([^{}]+)

Condition = _ 'if' _ '(' lhs:term '===' rhs:term ')' _ body: Code {
  return {condition: {lhs, rhs}, body}
}
term = $[^{}()=]+
_ "whitespace"
  = [ \t\n\r]*

For the condition part it will produce

  {
      "condition": {
         "lhs": "user.id ",
         "rhs": " 'abc123...'"
      },
      "body": [
         {
            "nested": [
               [
                  " function_name() "
               ]
            ]
         }
      ]
   }

Upvotes: 1

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