PEG Parser generator how to fix Expected "whitespace" but " " found

Question

I have a readable stream of text input (including unicode characters from html) from which I am trying to extract information by specifying the structure in PEG.js and returning custom JSON objects from matched items.

I have the text input in the following format -

1. some input [tags]
(a) some text (b) some text
Ans. (b) 

2. some input [tags]
(a) some text (b) some text
Ans. (b) 

So after searching for available node.js lexical parsers out there I found PEG and tried this sample script in their online version -

start
    = demo
_ "whitespace"
  = [ \t\n\r]*
demo
    = digits:[0-9]+."whitespace" "literal"+

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

But I am getting error -

"Line 1, column 3: Expected "whitespace" but " " found."

So, how can I include whitespaces in my expression Or, are there any better ways / libraries to accomplish this with node.js

Answer 1

You are using "whitespace" but you should be using _.

You can think of "whitespace" as a comment that explains what _ is supposed to mean.

peg.js should work fine in your case, as long as the input data is well formed.