delete.js

Google浏览器V8内核代码

// Copyright 2008 the V8 project authors. All rights reserved.
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
//       notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
//       copyright notice, this list of conditions and the following
//       disclaimer in the documentation and/or other materials provided
//       with the distribution.
//     * Neither the name of Google Inc. nor the names of its
//       contributors may be used to endorse or promote products derived
//       from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

// We use the has() function to avoid relying on a functioning
// implementation of 'in'.
function has(o, k) { return typeof o[k] !== 'undefined'; }

assertTrue(delete null);
assertTrue(delete 2);
assertTrue(delete 'foo');
assertTrue(delete Number(7));
assertTrue(delete new Number(8));

assertTrue(delete {}.x);
assertTrue(delete {}.y);
assertTrue(delete {}.toString);

x = 42;
assertEquals(42, x);
assertTrue(delete x);
assertTrue(typeof x === 'undefined', "x is gone");

/**** 
 * This test relies on DontDelete attributes. This is not 
 * working yet.

var y = 87; // should have DontDelete attribute
assertEquals(87, y);
assertFalse(delete y, "don't delete");
assertFalse(typeof y === 'undefined');
assertEquals(87, y);
*/

var o = { x: 42, y: 87 };
assertTrue(has(o, 'x'));
assertTrue(has(o, 'y'));
assertTrue(delete o.x);
assertFalse(has(o, 'x'));
assertTrue(has(o, 'y'));
assertTrue(delete o['y']);
assertFalse(has(o, 'x'));
assertFalse(has(o, 'y'));


var o = {};
for (var i = 0x0020; i < 0x02ff; i+=2) {
  o[String.fromCharCode(i)] = i;
  o[String.fromCharCode(i+1)] = i+1;
}
for (var i = 0x0020; i < 0x02ff; i+=2) {
  assertTrue(delete o[String.fromCharCode(i)]);
}
for (var i = 0x0020; i < 0x02ff; i+=2) {
  assertFalse(has(o, String.fromCharCode(i)), "deleted (" + i + ")");
  assertTrue(has(o, String.fromCharCode(i+1)), "still here (" + i + ")");
}


var a = [0,1,2];
assertTrue(has(a, 0));
assertTrue(delete a[0]);
assertFalse(has(a, 0), "delete 0");
assertEquals(1, a[1]);
assertEquals(2, a[2]);
assertTrue(delete a[100], "delete 100");
assertTrue(delete a[Math.pow(2,31)-1], "delete 2^31-1");
assertFalse(has(a, 0), "delete 0");
assertEquals(1, a[1]);
assertEquals(2, a[2]);


var a = [0,1,2];
assertEquals(3, a.length);
assertTrue(delete a[2]);
assertEquals(3, a.length);
assertTrue(delete a[0]);
assertEquals(3, a.length);
assertTrue(delete a[1]);
assertEquals(3, a.length);


var o = {};
o[Math.pow(2,30)-1] = 0;
o[Math.pow(2,31)-1] = 0;
o[1] = 0;
assertTrue(delete o[0]);
assertTrue(delete o[Math.pow(2,30)]);
assertFalse(has(o, 0), "delete 0");
assertFalse(has(o, Math.pow(2,30)));
assertTrue(has(o, 1));
assertTrue(has(o, Math.pow(2,30)-1));
assertTrue(has(o, Math.pow(2,31)-1));

assertTrue(delete o[Math.pow(2,30)-1]);
assertTrue(has(o, 1));
assertFalse(has(o, Math.pow(2,30)-1), "delete 2^30-1");
assertTrue(has(o, Math.pow(2,31)-1));

assertTrue(delete o[1]);
assertFalse(has(o, 1), "delete 1");
assertFalse(has(o, Math.pow(2,30)-1), "delete 2^30-1");
assertTrue(has(o, Math.pow(2,31)-1));

assertTrue(delete o[Math.pow(2,31)-1]);
assertFalse(has(o, 1), "delete 1");
assertFalse(has(o, Math.pow(2,30)-1), "delete 2^30-1");
assertFalse(has(o, Math.pow(2,31)-1), "delete 2^31-1");


var a = [];
a[Math.pow(2,30)-1] = 0;
a[Math.pow(2,31)-1] = 0;
a[1] = 0;
assertTrue(delete a[0]);
assertTrue(delete a[Math.pow(2,30)]);
assertFalse(has(a, 0), "delete 0");
assertFalse(has(a, Math.pow(2,30)), "delete 2^30");
assertTrue(has(a, 1));
assertTrue(has(a, Math.pow(2,30)-1));
assertTrue(has(a, Math.pow(2,31)-1));
assertEquals(Math.pow(2,31), a.length);

assertTrue(delete a[Math.pow(2,30)-1]);
assertTrue(has(a, 1));
assertFalse(has(a, Math.pow(2,30)-1), "delete 2^30-1");
assertTrue(has(a, Math.pow(2,31)-1));
assertEquals(Math.pow(2,31), a.length);

assertTrue(delete a[1]);
assertFalse(has(a, 1), "delete 1");
assertFalse(has(a, Math.pow(2,30)-1), "delete 2^30-1");
assertTrue(has(a, Math.pow(2,31)-1));
assertEquals(Math.pow(2,31), a.length);

assertTrue(delete a[Math.pow(2,31)-1]);
assertFalse(has(a, 1), "delete 1");
assertFalse(has(a, Math.pow(2,30)-1), "delete 2^30-1");
assertFalse(has(a, Math.pow(2,31)-1), "delete 2^31-1");
assertEquals(Math.pow(2,31), a.length);