lodash/math/sum.js

define(['../lang/isArray', '../internal/toIterable'], function(isArray, toIterable) {

  /**
   * Gets the sum of the values in `collection`.
   *
   * @static
   * @memberOf _
   * @category Math
   * @param {Array|Object|string} collection The collection to iterate over.
   * @returns {number} Returns the sum.
   * @example
   *
   * _.sum([4, 6, 2]);
   * // => 12
   *
   * _.sum({ 'a': 4, 'b': 6, 'c': 2 });
   * // => 12
   */
  function sum(collection) {
    if (!isArray(collection)) {
      collection = toIterable(collection);
    }
    var length = collection.length,
        result = 0;

    while (length--) {
      result += +collection[length] || 0;
    }
    return result;
  }

  return sum;
});