index.js

/**
 * @module transformProps.
 *
 * Some of these mini-functions were broken out to increase performance.
 */

/**
 * @param {mixed} memo is the current value of the prop.
 * @param {function} transformer is a function.
 * @return {mixed}
 */
function reducer(memo, transformer) {
  return transformer(memo);
}

/**
 * @param {object} object
 * @param {function[]} transformers
 * @param {string[]} propKeys
 * @param {string} k
 */
function forEachKey(object, transformers, propKeys, k) {
  var v = object[k];

  if (propKeys.hasOwnProperty(k)) {
    object[k] = transformers.reduce(reducer, v);
    return;
  }
  if (!(typeof v === 'object' && v !== null)) return;
  iterate(v, transformers, propKeys);
}

/**
 * @param {object} object
 * @param {function[]} transformers
 * @param {string[]} propKeys
 */
function iterate(object, transformers, propKeys) {
  Object.keys(object).forEach(forEachKey.bind(null, object, transformers, propKeys));
}

/**
 * @param {function | function[]} transformers
 */
function throwIfNotFuncOrAryOfFunc(transformers) {
  if (
    Array.isArray(transformers) && transformers.find(function find(item) {
      return typeof item !== 'function';
    })
    ||
    !Array.isArray(transformers) && typeof transformers !== 'function'
  ) {
    throw new TypeError('Expected @transformers to be a function or array of functions but received: "' + transformers + '".');
  }
}

/**
 * @param {object} object
 */
function throwIfNotObj(object) {
  if (!(typeof object === 'object' && object !== null)) {
    throw new TypeError('Expected @object to be an object but received: "' + object + '".');
  }
}

/**
 * @param {str | str[]} propKeys
 */
function throwIfNotStrOrAryOfStr(propKeys) {
  if (
    Array.isArray(propKeys) && propKeys.find(function find(item) {
      return typeof item !== 'string';
    })
    ||
    !Array.isArray(propKeys) && typeof propKeys !== 'string'
  ) {
    throw new TypeError('Expected @propKeys to be a string or array of strings but received: "' + propKeys + '".');
  }
}

/**
 * @param {object} object
 * @param {function[]} transformers
 * @param {string[]} propKeys
 * @return {object}
 */
function transformProps(object, transformers, propKeys) {
  throwIfNotObj(object);
  throwIfNotFuncOrAryOfFunc(transformers);
  throwIfNotStrOrAryOfStr(propKeys);
  transformers = Array.isArray(transformers) ? transformers : [transformers];
  propKeys = Array.isArray(propKeys) ? propKeys : [propKeys];
  propKeys = propKeys.reduce(function reduce(memo, propKey) {
    memo[propKey] = 1;
    return memo;
  }, {});
  iterate(object, transformers, propKeys);

  return object;
}

module.exports = transformProps;