text: 'use strict';
  
  var flatten = require('arr-flatten');
  var isNumber = require('is-number');
  
  /**
   * Returns the sum of all numbers in the given array.
   *
   * ```js
   * sum([1, 2, 3, 4, 5])
   * //=> '15'
   * ```
   *
   * @name .sum
   * @param {Array} `array` Array of numbers to add up.
   * @return {Number}
   * @api public
   */
  
  module.exports = function sum_() {
    var args = flatten([].concat.apply([], arguments));
    var i = args.length, sum = 0;
    while (i--) {
      if (!isNumber(args[i])) {
        continue;
      }
      sum += (+args[i]);
    }
    return sum;
  };
  