# Bug Fixes

Submitting our solution revealed a few bugs in our solution. The first
bug can be pointed out with this failing test:

    expect([].sameStructureAs(1)).to.be.false;

We were assuming that `other` would be an array. Unfortunately in this
case, `other` is `1`, which causes `_.zipWith` to return an empty array.

We can fix this bug by adding an upfront check asserting that `other` is
an `Array`.

After fixing that issue, another bug reared its ugly head:

    expect([1].sameStructureAs([1, 2])).to.be.false;

In the last iteration of `_.zipWith`, `a` was `undefined` and `b` was
`2`. While checking if both of these values were not arrays returned
true, we didn't check if both values existed.

The fix for this bug is to check that both `a` and `b` are not
`undefined`:

    let bothDefined = !_.isUndefined(a) && !_.isUndefined(b);
    let bothNot = bothDefined && !_.isArray(a) && !_.isArray(b);

With those fixes, out suite flips back to green!

index.js

@@ -1,9 +1,13 @@
 import _ from "lodash";
 
 Array.prototype.sameStructureAs = function(other) {
+    if (!_.isArray(other)) {
+        return false;
+    }
     let comparisons = _.zipWith(this, other, (a, b) => {
         let bothArrays = _.isArray(a) && _.isArray(b);
-        let bothNot = !_.isArray(a) && !_.isArray(b);
+        let bothDefined = !_.isUndefined(a) && !_.isUndefined(b);
+        let bothNot = bothDefined && !_.isArray(a) && !_.isArray(b);
         return (bothArrays && a.sameStructureAs(b)) || bothNot;
     });
     return _.every(comparisons);

test/index.js

@@ -10,6 +10,8 @@ describe("sameStructureAs", function() {
         expect([[], 1].sameStructureAs([[], []])).to.be.false;
         expect([[], [1]].sameStructureAs([[], [1]])).to.be.true;
         expect([[], [1]].sameStructureAs([[], [[]]])).to.be.false;
+        expect([].sameStructureAs(1)).to.be.false;
+        expect([1].sameStructureAs([1, 2])).to.be.false;
     });
 
 });