diff --git a/test/test_jsinterp.py b/test/test_jsinterp.py
index 75f29b2b5..6199594f6 100644
--- a/test/test_jsinterp.py
+++ b/test/test_jsinterp.py
@@ -542,6 +542,40 @@ class TestJSInterpreter(unittest.TestCase):
         self._test('function f(){return "012345678".slice(-1, 1)}', '')
         self._test('function f(){return "012345678".slice(-3, -1)}', '67')
 
+    def test_pop(self):
+        # pop
+        self._test('function f(){var a = [0, 1, 2, 3, 4, 5, 6, 7, 8]; return [a.pop(), a]}',
+                   [8, [0, 1, 2, 3, 4, 5, 6, 7]])
+        self._test('function f(){return [].pop()}', JS_Undefined)
+        # push
+        self._test('function f(){var a = [0, 1, 2]; return [a.push(3, 4), a]}',
+                   [5, [0, 1, 2, 3, 4]])
+        self._test('function f(){var a = [0, 1, 2]; return [a.push(), a]}',
+                   [3, [0, 1, 2]])
+
+    def test_shift(self):
+        # shift
+        self._test('function f(){var a = [0, 1, 2, 3, 4, 5, 6, 7, 8]; return [a.shift(), a]}',
+                   [0, [1, 2, 3, 4, 5, 6, 7, 8]])
+        self._test('function f(){return [].shift()}', JS_Undefined)
+        # unshift
+        self._test('function f(){var a = [0, 1, 2]; return [a.unshift(3, 4), a]}',
+                   [5, [3, 4, 0, 1, 2]])
+        self._test('function f(){var a = [0, 1, 2]; return [a.unshift(), a]}',
+                   [3, [0, 1, 2]])
+
+    def test_forEach(self):
+        self._test('function f(){var ret = []; var l = [4, 2]; '
+                   'var log = function(e,i,a){ret.push([e,i,a]);}; '
+                   'l.forEach(log); '
+                   'return [ret.length, ret[0][0], ret[1][1], ret[0][2]]}',
+                   [2, 4, 1, [4, 2]])
+        self._test('function f(){var ret = []; var l = [4, 2]; '
+                   'var log = function(e,i,a){this.push([e,i,a]);}; '
+                   'l.forEach(log, ret); '
+                   'return [ret.length, ret[0][0], ret[1][1], ret[0][2]]}',
+                   [2, 4, 1, [4, 2]])
+
 
 if __name__ == '__main__':
     unittest.main()
diff --git a/youtube_dl/jsinterp.py b/youtube_dl/jsinterp.py
index bec959946..0cfae4b28 100644
--- a/youtube_dl/jsinterp.py
+++ b/youtube_dl/jsinterp.py
@@ -1113,37 +1113,31 @@ class JSInterpreter(object):
                     index, how_many = map(int, (argvals + [len(obj)])[:2])
                     if index < 0:
                         index += len(obj)
-                    add_items = argvals[2:]
-                    res = []
-                    for _ in range(index, min(index + how_many, len(obj))):
-                        res.append(obj.pop(index))
-                    for i, item in enumerate(add_items):
-                        obj.insert(index + i, item)
+                    res = [obj.pop(index)
+                           for _ in range(index, min(index + how_many, len(obj)))]
+                    obj[index:index] = argvals[2:]
                     return res
-                elif member == 'unshift':
-                    assertion(isinstance(obj, list), 'must be applied on a list')
-                    assertion(argvals, 'takes one or more arguments')
-                    for item in reversed(argvals):
-                        obj.insert(0, item)
-                    return obj
-                elif member == 'pop':
+                elif member in ('shift', 'pop'):
                     assertion(isinstance(obj, list), 'must be applied on a list')
                     assertion(not argvals, 'does not take any arguments')
-                    if not obj:
-                        return
-                    return obj.pop()
+                    return obj.pop(0 if member == 'shift' else -1) if len(obj) > 0 else JS_Undefined
+                elif member == 'unshift':
+                    assertion(isinstance(obj, list), 'must be applied on a list')
+                    # not enforced: assertion(argvals, 'takes one or more arguments')
+                    obj[0:0] = argvals
+                    return len(obj)
                 elif member == 'push':
-                    assertion(argvals, 'takes one or more arguments')
+                    # not enforced: assertion(argvals, 'takes one or more arguments')
                     obj.extend(argvals)
-                    return obj
+                    return len(obj)
                 elif member == 'forEach':
                     assertion(argvals, 'takes one or more arguments')
-                    assertion(len(argvals) <= 2, 'takes at-most 2 arguments')
+                    assertion(len(argvals) <= 2, 'takes at most 2 arguments')
                     f, this = (argvals + [''])[:2]
                     return [f((item, idx, obj), {'this': this}, allow_recursion) for idx, item in enumerate(obj)]
                 elif member == 'indexOf':
                     assertion(argvals, 'takes one or more arguments')
-                    assertion(len(argvals) <= 2, 'takes at-most 2 arguments')
+                    assertion(len(argvals) <= 2, 'takes at most 2 arguments')
                     idx, start = (argvals + [0])[:2]
                     try:
                         return obj.index(idx, start)
@@ -1152,7 +1146,7 @@ class JSInterpreter(object):
                 elif member == 'charCodeAt':
                     assertion(isinstance(obj, compat_str), 'must be applied on a string')
                     # assertion(len(argvals) == 1, 'takes exactly one argument') # but not enforced
-                    idx = argvals[0] if isinstance(argvals[0], int) else 0
+                    idx = argvals[0] if len(argvals) > 0 and isinstance(argvals[0], int) else 0
                     if idx >= len(obj):
                         return None
                     return ord(obj[idx])