tech(array): flatMap method by example

Author: shangan23

array/flatMap.js

@@ -0,0 +1,37 @@
+//Understanding Array.prototype.flatMap()
+//   myArray.map().flat(1) - equivalent
+
+let movies = [
+  'Dog Soldiers',
+  ['In Bruges', 'From Paris with Love', 'Layer Cake'],
+  'The Big Lebowski',
+  '',
+  '    ',
+  'Memento, The Platform,Fight Club, ',
+  'Hotel Rwanda, Moon, Under the Skin',
+  'Lady Bird',
+  ['Platoon', 'Wall-E'],
+]
+let arr = movies.flatMap((entry) => {
+  if (Array.isArray(entry)) {
+    return entry
+  } else if (typeof entry === 'string' && entry.trim() === '') {
+    return [] //remove the empty strings
+  } else {
+    //other strings
+    return entry
+      .split(',')
+      .map((txt) => txt.trim())
+      .filter((txt) => txt != '')
+  }
+})
+console.log(arr)
+
+let strings = ["one","two","three"]
+let numbers = [1,2,3]
+
+//let mappedStringNumber = numbers.map((val, idx) => [val, strings[idx]]) //[ [ 1, 'one' ], [ 2, 'two' ], [ 3, 'three' ] ]
+let mappedStringNumber = numbers.flatMap((val, idx) => [val, strings[idx]]) //[ 1, 'one', 2, 'two', 3, 'three' ]
+console.log(mappedStringNumber)
+
+