codenamezjames · January 1, 2019 16:15 · Jan 1, 2019
diff --git a/flatten.js b/flatten.js
@@ -0,0 +1,28 @@
+function flatten(arr, depth = Infinity, result = []) {
+  if(!Array.isArray(arr)) return null
+  for (const value of arr) {
+    if (depth > 0 && Array.isArray(value)) {
+      if (depth > 1) {
+        flatten(value, depth - 1, result)
+      } else {
+        result.push(...value)
+      }
+    } else {
+      result[result.length] = value
+    }
+  }
+  return result
+}
+
+
+// Tests
+const superFlat = JSON.stringify(flatten( [[ [[[[1]]]], 2, [ 3 ] ], 4] )) === JSON.stringify([1, 2, 3, 4])
+if ( !superFlat ) throw 'Failed to flatten many layers deep'
+
+const oneLayer = JSON.stringify(flatten( [1,2,3,[[4]]], 1 )) === JSON.stringify([1,2,3,[4]])
+if (!oneLayer) throw 'Failed to only flatten one layer'
+
+const crazyInput = JSON.stringify(flatten( {1:1, 2:2, 3:3} )) === JSON.stringify(null)
+if(!crazyInput) throw 'Does not handle crazy inputs'
+
+console.log('Everything flattened successfully')