[JS][7kyu] Composing squared strings

codewars/7kyu/composing-squared-strings/koronya.js

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+// [JS][7kyu] Composing squared strings
+// composing-squared-strings
+// https://www.codewars.com/kata/56f253dd75e340ff670002ac/train/javascript
+
+const compose = (s1, s2) => {
+  const arr1 = s1.split('\n')
+  const arr2 = s2.split('\n')
+  const n = arr1.length
+  const result = []
+
+  for (let i = 0; i < n; i += 1 || 0) {
+    const str1 = arr1[i]
+    const str2 = arr2[n - 1 - i]
+    result.push(`${str1.substring(0, i + 1)}${str2.substring(0, n - i)}`)
+  }
+
+  return result.join('\n')
+}
+
+compose('abcd\nefgh\nijkl\nmnop', 'qrst\nuvwx\nyz12\n3456') === 'a3456\nefyz1\nijkuv\nmnopq'
+compose('byGt\nhTts\nRTFF\nCnnI', 'jIRl\nViBu\nrWOb\nNkTB') === 'bNkTB\nhTrWO\nRTFVi\nCnnIj'
+compose('HXxA\nTGBf\nIPhg\nuUMD', 'Hcbj\nqteH\nGbMJ\ngYPW') === 'HgYPW\nTGGbM\nIPhqt\nuUMDH'
+compose('tSrJ\nOONy\nsqPF\nxMkB', 'hLqw\nEZuh\nmYFl\nzlYf') === 'tzlYf\nOOmYF\nsqPEZ\nxMkBh'
+