index.js #1

/**
 * lodash 3.0.1 (Custom Build) <https://lodash.com/>
 * Build: `lodash modern modularize exports="npm" -o ./`
 * Copyright 2012-2015 The Dojo Foundation <http://dojofoundation.org/>
 * Based on Underscore.js 1.8.3 <http://underscorejs.org/LICENSE>
 * Copyright 2009-2015 Jeremy Ashkenas, DocumentCloud and Investigative Reporters & Editors
 * Available under MIT license <https://lodash.com/license>
 */

/**
 * A specialized version of `baseCallback` which only supports `this` binding
 * and specifying the number of arguments to provide to `func`.
 *
 * @private
 * @param {Function} func The function to bind.
 * @param {*} thisArg The `this` binding of `func`.
 * @param {number} [argCount] The number of arguments to provide to `func`.
 * @returns {Function} Returns the callback.
 */
function bindCallback(func, thisArg, argCount) {
  if (typeof func != 'function') {
    return identity;
  }
  if (thisArg === undefined) {
    return func;
  }
  switch (argCount) {
    case 1: return function(value) {
      return func.call(thisArg, value);
    };
    case 3: return function(value, index, collection) {
      return func.call(thisArg, value, index, collection);
    };
    case 4: return function(accumulator, value, index, collection) {
      return func.call(thisArg, accumulator, value, index, collection);
    };
    case 5: return function(value, other, key, object, source) {
      return func.call(thisArg, value, other, key, object, source);
    };
  }
  return function() {
    return func.apply(thisArg, arguments);
  };
}

/**
 * This method returns the first argument provided to it.
 *
 * @static
 * @memberOf _
 * @category Utility
 * @param {*} value Any value.
 * @returns {*} Returns `value`.
 * @example
 *
 * var object = { 'user': 'fred' };
 *
 * _.identity(object) === object;
 * // => true
 */
function identity(value) {
  return value;
}

module.exports = bindCallback;