stalmok · February 11, 2019 01:34 · Feb 11, 2019
diff --git a/flatten.js b/flatten.js
@@ -0,0 +1,45 @@
+/**
+ * Code was written in Javascript (ES6)
+ * Tests will work only in Node.js environment
+ */
+
+/**
+ * Flatten an array of arbitrarily nested arrays of integers into
+ * a flat array of integers. e.g. [[1,2,[3]],4] -> [1,2,3,4].
+ *
+ * @param {Array} input
+ */
+function flatten(input) {
+  if (!Array.isArray(input)) {
+    throw TypeError(`An Array is expected, ${typeof input} was given.`);
+  }
+
+  let result = [];
+
+  input.forEach(element => {
+    result.push(...(Array.isArray(element) ? flatten(element) : [element]));
+  });
+
+  return result;
+}
+
+/** Tests */
+const assert = require('assert');
+
+assert.throws(() => flatten(), TypeError);
+assert.throws(() => flatten(null), TypeError);
+assert.throws(() => flatten(1), TypeError);
+assert.throws(() => flatten('string'), TypeError);
+assert.throws(() => flatten(false), TypeError);
+assert.throws(() => flatten({}), TypeError);
+assert.throws(() => flatten(NaN), TypeError);
+assert.throws(() => flatten(Symbol()), TypeError);
+assert.throws(() => flatten(() => {}), TypeError);
+
+assert.deepEqual(flatten([]), []);
+assert.deepEqual(flatten([1, 2, 3]), [1, 2, 3]);
+assert.deepEqual(flatten([1, 2, [3]]), [1, 2, 3]);
+assert.deepEqual(flatten([1, 2, [3, [4]]]), [1, 2, 3, 4]);
+assert.deepEqual(flatten([[1, 2, [3]], 4]), [1, 2, 3, 4]);
+assert.deepEqual(flatten([[1, 2, 3, 4]]), [1, 2, 3, 4]);
+assert.deepEqual(flatten([[[[[1]]]]]), [1]);
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