[jsinterp] Support if statements

Closes #6131

test/test_jsinterp.py

@@ -155,6 +155,38 @@ class TestJSInterpreter(unittest.TestCase):
         self.assertEqual(jsi.call_function('z'), 5)
         self.assertEqual(jsi.call_function('y'), 2)
 
+    def test_if(self):
+        jsi = JSInterpreter('''
+        function x() {
+            let a = 9;
+            if (0==0) {a++}
+            return a
+        }''')
+        self.assertEqual(jsi.call_function('x'), 10)
+
+        jsi = JSInterpreter('''
+        function x() {
+            if (0==0) {return 10}
+        }''')
+        self.assertEqual(jsi.call_function('x'), 10)
+
+        jsi = JSInterpreter('''
+        function x() {
+            if (0!=0) {return 1}
+            else {return 10}
+        }''')
+        self.assertEqual(jsi.call_function('x'), 10)
+
+        """  # Unsupported
+        jsi = JSInterpreter('''
+        function x() {
+            if (0!=0) {return 1}
+            else if (1==0) {return 2}
+            else {return 10}
+        }''')
+        self.assertEqual(jsi.call_function('x'), 10)
+        """
+
     def test_for_loop(self):
         jsi = JSInterpreter('''
         function x() { a=0; for (i=0; i-10; i++) {a++} return a }

test/test_youtube_signature.py

@@ -134,6 +134,10 @@ _NSIG_TESTS = [
         'https://www.youtube.com/s/player/7a062b77/player_ias.vflset/en_US/base.js',
         'NRcE3y3mVtm_cV-W', 'VbsCYUATvqlt5w',
     ),
+    (
+        'https://www.youtube.com/s/player/dac945fd/player_ias.vflset/en_US/base.js',
+        'o8BkRxXhuYsBCWi6RplPdP', '3Lx32v_hmzTm6A',
+    ),
 ]