Sums all the values in an array by reducing it

sumValues.js

/**
 * Sums all the values in an array by reducing it.
 *
 * @param  {Array} array: the collection to iterate
 * @param  {String | Number} prop: (optional) property name or array index
 * @return {Number}
 */
function sumValues(array, prop) {
  if (!array || !array.length) return 0;
  if ((/string|number/).test(typeof prop)) {
    return array.reduce((total, cv) => total + (+cv[prop]), 0);
  }
  return array.reduce((total, cv) => total + (+cv), 0);
}

test.js

// reduces an array of numbers and sums all its values
var list = [1, 2, 3, 4, 5];
sumValues(list); // => 15

// reduces an array of string-numbers and sums all its values
list = ['1', '2', '3', '4', '5'];
sumValues(list); // => 15

// sums all values in the property "quantity"
list = [
  {id:12345, type:"a", quantity:10},
  {id:13458, type:"b", quantity:15},
  {id:12765, type:"x", quantity:12},
];
sumValues(list, "quantity"); // => 37

//sums all values at the index 2
list = [
  [12345, "tomb-raider", 4],
  [12346, "serious-sam", 1],
  [12765, "half-life", 3],
  [12766, "deus-ex", 2],
];
sumValues(list, 2); // => 10