What is the method of extracting solely the subitems from an array?

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One method to extract solely the subitems from an array is to use the array method "flatMap". The "flatMap" method combines the processing of "map" and "flatten" by applying a transformation function to each element in the array and then flattening the result into a new array. Here is an example code snippet using "flatMap" to extract the subitems from an array:

const items = [
  { id: 1, subitems: ['a', 'b', 'c'] },
  { id: 2, subitems: ['d', 'e', 'f'] },
  { id: 3, subitems: ['g', 'h', 'i'] }
];

const subitems = items.flatMap(item => item.subitems);

console.log(subitems); // ["a", "b", "c", "d", "e", "f", "g", "h", "i"]

In this example, the "flatMap" method iterates over each object in the "items" array and returns a new array containing only the subitems.