check typeof length

collection has also already been compared with null, so that check is
not needed.

index.js

@@ -13,7 +13,7 @@ module.exports = function toArray(collection) {
   if (collection === window) return [window]
   if (typeof collection === 'string') return [collection]
   if (Array.isArray(collection)) return collection.slice()
-  if (collection !== null && !collection.length) return [collection]
+  if (typeof collection.length != 'number') return [collection]
   if (typeof collection === 'function') return [collection]
   var arr = []
   for (var i = 0; i < collection.length; i++) {

test/to-array.js

@@ -35,6 +35,9 @@ describe('non-collections', function() {
   it('single element is empty for undefined', function() {
     assert.deepEqual([], toArray(undefined));
   })
+  it('detects `{length: true}` is not a collection', function() {
+    assert.deepEqual([{length: true}], toArray({length: true}));
+  })
 })
 
 describe('identifying collections', function() {