learn_enough_javascript_code_listings/Listing_6.9.js

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// lengths: Imperative solution
function imperativeLengths(elements) {
  let lengths = {};
  elements.forEach(function(element) {
    lengths[element] = element.length;
  });
  return lengths;
}
console.log(imperativeLengths(states));

// lengths: Functional solution
function functionalLengths(elements) {
  return elements.reduce((lengths, element) => {
                          lengths[element] = element.length;
                          return lengths;
                        }, {});
}
console.log(functionalLengths(states));