revive-functions/revive-functions.mjs

JSON reviver, allowing named functions and their parameters to be replaced by their output values

/**
 * JSON.parse reviver function which substitutes function tags with parameters for their output
 */
export const reviveFunctions = ({
  functions = { }, /* e.g add: (x,y) => x+y */
  getFunctionTag = f => '$' + f,
  bindDataToFunction = false,
  callFunctionsReturnedWithData = true
} = {},
data = undefined
) => function reviveFunctionsInner (key, item) {
  if (typeof item === 'object' && item != null && !Array.isArray(item)) {
    const [firstKey, args] = Object.entries(item)?.[0] ?? []
    const func = Object.entries(functions)
      .find(([key, f]) => getFunctionTag(key) === firstKey)
      ?.[1]
    if (firstKey && func && Object.keys(item).length === 1) {
      const funcRes = (bindDataToFunction ? func.bind(data) : func)( // call the function
        ...(
          [].concat(args) // allow single arg without array
            .map(arg => reviveFunctionsInner(null, arg)) // argument recursion
        )
      )
      // optional data as curried last argument:
      return (callFunctionsReturnedWithData && typeof (funcRes) === 'function')
        ? funcRes(data)
        : funcRes
    }
  };
  return item // default to unmodified
}

/**
 * Reviver function which substitutes function tags with parameters for their output
 * in a given JSON like structure, with optional data argument applied last to
 * curried functions
 */
export const reviveFunctionsInObject = ({
  functions = { /* e.g add: (x,y) => x+y */ },
  getFunctionTag = f => '$' + f,
  stringifyFirst = undefined,
  bindDataToFunction = false,
  callFunctionsReturnedWithData = true
} = {},
jsonLikeObject = {},
data = undefined
) => {
  if (Object.keys(functions).length === 0) {
    console.warn('Warning: ReviveFunctions: No functions provided')
  }
  return JSON.parse(
    (stringifyFirst || (typeof jsonLikeObject === 'object' && stringifyFirst == null))
      ? JSON.stringify(jsonLikeObject)
      : jsonLikeObject,
    reviveFunctions({
      functions,
      getFunctionTag,
      bindDataToFunction,
      callFunctionsReturnedWithData
    }, data)
  )
}

/**
 * Reviver function which substitutes function tags with parameters for their output
 * in a given JSON like structure, with curried object and data arguments
 */
export const reviveFunctionsInObjectCurried = (spec = {}) =>
  jsonLikeObject => data => reviveFunctionsInObject(spec, jsonLikeObject, data)