lodash.mean/index.js

The lodash method `_.mean` exported as a module.

/**
 * lodash 4.1.0 (Custom Build) <https://lodash.com/>
 * Build: `lodash modularize exports="npm" -o ./`
 * Copyright jQuery Foundation and other contributors <https://jquery.org/>
 * Released under MIT license <https://lodash.com/license>
 * Based on Underscore.js 1.8.3 <http://underscorejs.org/LICENSE>
 * Copyright Jeremy Ashkenas, DocumentCloud and Investigative Reporters & Editors
 */

/** Used as references for various `Number` constants. */
var NAN = 0 / 0;

/**
 * The base implementation of `_.mean` and `_.meanBy` without support for
 * iteratee shorthands.
 *
 * @private
 * @param {Array} array The array to iterate over.
 * @param {Function} iteratee The function invoked per iteration.
 * @returns {number} Returns the mean.
 */
function baseMean(array, iteratee) {
  var length = array ? array.length : 0;
  return length ? (baseSum(array, iteratee) / length) : NAN;
}

/**
 * The base implementation of `_.sum` and `_.sumBy` without support for
 * iteratee shorthands.
 *
 * @private
 * @param {Array} array The array to iterate over.
 * @param {Function} iteratee The function invoked per iteration.
 * @returns {number} Returns the sum.
 */
function baseSum(array, iteratee) {
  var result,
      index = -1,
      length = array.length;

  while (++index < length) {
    var current = iteratee(array[index]);
    if (current !== undefined) {
      result = result === undefined ? current : (result + current);
    }
  }
  return result;
}

/**
 * This method returns the first argument given to it.
 *
 * @static
 * @since 0.1.0
 * @memberOf _
 * @category Util
 * @param {*} value Any value.
 * @returns {*} Returns `value`.
 * @example
 *
 * var object = { 'user': 'fred' };
 *
 * _.identity(object) === object;
 * // => true
 */
function identity(value) {
  return value;
}

/**
 * Computes the mean of the values in `array`.
 *
 * @static
 * @memberOf _
 * @since 4.0.0
 * @category Math
 * @param {Array} array The array to iterate over.
 * @returns {number} Returns the mean.
 * @example
 *
 * _.mean([4, 2, 8, 6]);
 * // => 5
 */
function mean(array) {
  return baseMean(array, identity);
}

module.exports = mean;