lodash/internal/baseCallback.js

var baseMatches = require('./baseMatches'),
    baseMatchesProperty = require('./baseMatchesProperty'),
    baseProperty = require('./baseProperty'),
    bindCallback = require('./bindCallback'),
    identity = require('../utility/identity');

/**
 * The base implementation of `_.callback` which supports specifying the
 * number of arguments to provide to `func`.
 *
 * @private
 * @param {*} [func=_.identity] The value to convert to a callback.
 * @param {*} [thisArg] The `this` binding of `func`.
 * @param {number} [argCount] The number of arguments to provide to `func`.
 * @returns {Function} Returns the callback.
 */
function baseCallback(func, thisArg, argCount) {
  var type = typeof func;
  if (type == 'function') {
    return typeof thisArg == 'undefined'
      ? func
      : bindCallback(func, thisArg, argCount);
  }
  if (func == null) {
    return identity;
  }
  if (type == 'object') {
    return baseMatches(func);
  }
  return typeof thisArg == 'undefined'
    ? baseProperty(func + '')
    : baseMatchesProperty(func + '', thisArg);
}

module.exports = baseCallback;