Add support of array initialization like [1,,,'4']

src/libjsparser/parser.c

@@ -890,8 +890,21 @@ parse_argument_list (argument_list_type alt, idx_t obj)
         STACK_PUSH (IDX, token_data ());
         break;
       }
-      case AL_FUNC_EXPR:
       case AL_ARRAY_DECL:
+      {
+        if (token_is (TOK_COMMA))
+        {
+          STACK_PUSH (IDX, next_temp_name ());
+          DUMP_OPCODE_3 (assignment, ID(1), OPCODE_ARG_TYPE_SIMPLE, ECMA_SIMPLE_VALUE_UNDEFINED);
+          DUMP_OPCODE_3 (meta, OPCODE_META_TYPE_VARG, ID(1), INVALID_VALUE);
+          STACK_INCR_HEAD(U8, 1);
+          STACK_DROP (IDX, 1);
+          skip_newlines ();
+          continue;
+        }
+        /* FALLTHRU  */
+      }
+      case AL_FUNC_EXPR:
       case AL_CONSTRUCT_EXPR:
       {
         parse_assignment_expression ();

src/liboptimizer/pretty-printer.c

@@ -156,6 +156,9 @@ dump_variable (idx_t id)
         case ECMA_SIMPLE_VALUE_TRUE: \
           __printf ("true"); \
           break; \
+        case ECMA_SIMPLE_VALUE_UNDEFINED: \
+          __printf ("undefined"); \
+          break; \
         default: \
           JERRY_UNREACHABLE (); \
       } \

tests/jerry/array.js

@@ -71,3 +71,9 @@ assert(Array.prototype.length === 0);
 Array.prototype[0] = 'string value';
 assert(Array.prototype.length === 1);
 assert(Array.prototype[0] === 'string value');
+
+var c = [0,,,'3'];
+assert (c[0] === 0);
+assert (c[1] === undefined);
+assert (c[2] === undefined);
+assert (c[3] === '3');