The JavaScript .map method

[1, 2, 3]     // An array (or any type)
  .map(       // method name
    item,     // single array element
    index,    // current elemet index
    () => {}  // function to be sequentially applied to each element (must return a result)
  )

const integers = [1, 2, 3, 4, 5].map((item) => item * 2)
// [2, 4, 6, 8, 10]

const strings = ["one", "two", "three"].map((item, index) => `${index + 1} ${item}`)
// ["1 one", "2 two", "3 three"]

const mixedTypes = [undefined, null, "foo", 123, NaN, Symbol].map((item) => typeof item)
// ["undefined", "object", "string", "number", "number", "function"]

[1, 2, 3, 4].map((item) => {

  const evenOrOdd = item % 2 > 0 ? "odd" : "even"
  console.log(`${item} is ${evenOrOdd}`)
  
  return evenOrOdd
})

// 1 is odd
// 2 is even
// 3 is odd
// 4 is even
// ["odd", "even", "odd", "even"]