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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 // Test const properties and pre/postfix operation.
     29 function f() {
     30   const x = 1;
     31   x++;
     32   assertEquals(1, x);
     33   x--;
     34   assertEquals(1, x);
     35   ++x;
     36   assertEquals(1, x);
     37   --x;
     38   assertEquals(1, x);
     39   assertEquals(1, x++);
     40   assertEquals(1, x--);
     41   assertEquals(2, ++x);
     42   assertEquals(0, --x);
     43 }
     44 
     45 f();
     46 
     47 // Test that the value is read eventhough assignment is disallowed.
     48 // Spidermonkey does not do this, but it seems like the right thing to
     49 // do so that 'o++' is equivalent to 'o = o + 1'.
     50 var valueOfCount = 0;
     51 
     52 function g() {
     53   const o = { valueOf: function() { valueOfCount++; return 42; } };
     54   assertEquals(42, +o);
     55   assertEquals(1, valueOfCount);
     56   o++;
     57   assertEquals(42, +o);
     58   assertEquals(3, valueOfCount);
     59   ++o;
     60   assertEquals(42, +o);
     61   assertEquals(5, valueOfCount);
     62   o--;
     63   assertEquals(42, +o);
     64   assertEquals(7, valueOfCount);
     65   --o;
     66   assertEquals(42, +o);
     67   assertEquals(9, valueOfCount);
     68 }
     69 
     70 g();
     71