Solve InterviewCake's merge sorted arrays question

Write a function merging two sorted arrays into one sorted array.

scratch/deepmind/part_two/merge-sorted-arrays.ts

@@ -0,0 +1,63 @@
+function mergeArrays(xs: Array<number>, ys: Array<number>): Array<number> {
+  let i = 0;
+  let j = 0;
+  const result = [];
+
+  for (let q = 0; q < xs.length + ys.length; q += 1) {
+    if (i === xs.length) {
+      while (j < ys.length) {
+        result.push(ys[j]);
+        j += 1;
+      }
+    } else if (j === ys.length) {
+      while (i < xs.length) {
+        result.push(xs[i]);
+        i += 1;
+      }
+    } else if (xs[i] < ys[j]) {
+      result.push(xs[i]);
+      i += 1;
+    } else {
+      result.push(ys[j]);
+      j += 1;
+    }
+  }
+
+  return result;
+}
+
+// Tests
+let desc = "both arrays are empty";
+let actual = mergeArrays([], []);
+let expected = [];
+assertDeepEqual(actual, expected, desc);
+
+desc = "first array is empty";
+actual = mergeArrays([], [1, 2, 3]);
+expected = [1, 2, 3];
+assertDeepEqual(actual, expected, desc);
+
+desc = "second array is empty";
+actual = mergeArrays([5, 6, 7], []);
+expected = [5, 6, 7];
+assertDeepEqual(actual, expected, desc);
+
+desc = "both arrays have some numbers";
+actual = mergeArrays([2, 4, 6], [1, 3, 7]);
+expected = [1, 2, 3, 4, 6, 7];
+assertDeepEqual(actual, expected, desc);
+
+desc = "arrays are different lengths";
+actual = mergeArrays([2, 4, 6, 8], [1, 7]);
+expected = [1, 2, 4, 6, 7, 8];
+assertDeepEqual(actual, expected, desc);
+
+function assertDeepEqual(a: Array<number>, b: Array<number>, desc: string) {
+  const aStr = JSON.stringify(a);
+  const bStr = JSON.stringify(b);
+  if (aStr !== bStr) {
+    console.log(`${desc} ... FAIL: ${aStr} != ${bStr}`);
+  } else {
+    console.log(`${desc} ... PASS`);
+  }
+}