Array.from: add (and fix) tests ensuring a falsy thisArg is accepted.

paulmillr · Aug 6, 2014 · 14df918 · 14df918
1 parent 22e01c3
commit 14df918
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Showing 2 changed files with 10 additions and 2 deletions.
diff --git a/es6-shim.js b/es6-shim.js
@@ -572,7 +572,8 @@
           throw new TypeError('Array.from: when provided, the second argument must be a function');
         }
 
-        var thisArg = arguments.length > 2 ? arguments[2] : undefined;
+        var hasThisArg = arguments.length > 2;
+        var thisArg = hasThisArg ? arguments[2] : undefined;
 
         var usingIterator = ES.IsIterable(list);
         // does the spec really mean that Arrays should use ArrayIterator?
@@ -595,7 +596,7 @@
             value = list[i];
           }
           if (mapFn) {
-            result[i] = thisArg ? mapFn.call(thisArg, value, i) : mapFn(value, i);
+            result[i] = hasThisArg ? mapFn.call(thisArg, value, i) : mapFn(value, i);
           } else {
             result[i] = value;
           }

diff --git a/test/array.js b/test/array.js
@@ -151,6 +151,13 @@ var runArrayTests = function() {
             expect(Object.prototype.toString.call(this)).to.equal('[object Number]');
           }, 42);
         });
+
+        it('accepts a falsy thisArg', function () {
+          Array.from([1, 2, 3], function (value, index) {
+            expect(this.valueOf()).to.equal(false);
+            expect(Object.prototype.toString.call(this)).to.equal('[object Boolean]');
+          }, false);
+        });
       });
 
       it('throws when provided a nonfunction second arg', function() {