Function peek

peek<TToken, TOptions, TValue>(p: Matcher<TToken, TOptions, TValue>, f: ((r: Match<TValue>, data: Data<TToken, TOptions>, i: number) => void)): Matcher<TToken, TOptions, TValue>
This overload adds a side effect to a Matcher without changing it's result.

Use action if there is nothing to wrap and you need a non-consuming parser instead.
Type Parameters
- TToken
- TOptions
- TValue
Parameters
- p: Matcher<TToken, TOptions, TValue>
  
  A matcher.
- f: ((r: Match<TValue>, data: Data<TToken, TOptions>, i: number) => void)
  
  A function to produce a side effect (logging, etc).
  - - (r: Match<TValue>, data: Data<TToken, TOptions>, i: number): void
    - Parameters
      
      r: Match<TValue>
      
      A Result object after running the base parser.
      
      data: Data<TToken, TOptions>
      
      Data object (tokens and options).
      
      i: number
      
      Parser position in the tokens array (before the first parser matched).
      
      Returns void
Returns Matcher<TToken, TOptions, TValue>
peek<TToken, TOptions, TValue>(p: Parser<TToken, TOptions, TValue>, f: ((r: Result<TValue>, data: Data<TToken, TOptions>, i: number) => void)): Parser<TToken, TOptions, TValue>
Add a side effect to a parser without changing it's result.

Use action if there is nothing to wrap and you need a non-consuming parser instead.
Type Parameters
- TToken
- TOptions
- TValue
Parameters
- p: Parser<TToken, TOptions, TValue>
  
  A parser.
- f: ((r: Result<TValue>, data: Data<TToken, TOptions>, i: number) => void)
  
  A function to produce a side effect (logging, etc).
  - - (r: Result<TValue>, data: Data<TToken, TOptions>, i: number): void
    - Parameters
      
      r: Result<TValue>
      
      A Result object after running the base parser.
      
      data: Data<TToken, TOptions>
      
      Data object (tokens and options).
      
      i: number
      
      Parser position in the tokens array (before the first parser matched).
      
      Returns void
Returns Parser<TToken, TOptions, TValue>

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