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      1 // Copyright 2008 the V8 project authors. All rights reserved.
      2 // Redistribution and use in source and binary forms, with or without
      3 // modification, are permitted provided that the following conditions are
      4 // met:
      5 //
      6 //     * Redistributions of source code must retain the above copyright
      7 //       notice, this list of conditions and the following disclaimer.
      8 //     * Redistributions in binary form must reproduce the above
      9 //       copyright notice, this list of conditions and the following
     10 //       disclaimer in the documentation and/or other materials provided
     11 //       with the distribution.
     12 //     * Neither the name of Google Inc. nor the names of its
     13 //       contributors may be used to endorse or promote products derived
     14 //       from this software without specific prior written permission.
     15 //
     16 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     17 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     18 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
     19 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
     20 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     21 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
     22 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     23 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     24 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     25 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     26 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     27 
     28 // const variables should be read-only
     29 const c = 42;
     30 c = 87;
     31 assertEquals(42, c);
     32 
     33 
     34 // const variables are not behaving like other JS variables when it comes
     35 // to scoping - in fact they behave more sanely. Inside a 'with' they do
     36 // not interfere with the 'with' scopes.
     37 
     38 (function () {
     39   with ({ x: 42 }) {
     40     const x = 7;
     41   }
     42   x = 5;
     43   assertEquals(7, x);
     44 })();
     45 
     46 
     47 // const variables may be declared but never initialized, in which case
     48 // their value is undefined.
     49 
     50 (function (sel) {
     51   if (sel == 0)
     52     with ({ x: 42 }) {
     53     const x;
     54     }
     55   else
     56     x = 3;
     57   x = 5;
     58   assertTrue(typeof x == 'undefined');
     59 })(1);
     60 
     61 
     62 // const variables may be initialized to undefined.
     63 (function () {
     64   with ({ x: 42 }) {
     65     const x = undefined;
     66   }
     67   x = 5;
     68   assertTrue(typeof x == 'undefined');
     69 })();
     70 
     71 
     72 // const variables may be accessed in inner scopes like any other variable.
     73 (function () {
     74   function bar() {
     75     assertEquals(7, x);
     76   }
     77   with ({ x: 42 }) {
     78     const x = 7;
     79   }
     80   x = 5
     81   bar();
     82 })();
     83 
     84 
     85 // const variables may be declared via 'eval'
     86 (function () {
     87   with ({ x: 42 }) {
     88     eval('const x = 7');
     89   }
     90   x = 5;
     91   assertEquals(7, x);
     92 })();
     93