v8/test/mjsunit/array-join.js

// Copyright 2008 the V8 project authors. All rights reserved.
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// modification, are permitted provided that the following conditions are
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//
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// Test that array join calls toString on subarrays.
var a = [[1,2],3,4,[5,6]];
assertEquals('1,2345,6', a.join(''));
assertEquals('1,2*3*4*5,6', a.join('*'));
assertEquals('1,2**3**4**5,6', a.join('**'));
assertEquals('1,2****3****4****5,6', a.join('****'));
assertEquals('1,2********3********4********5,6', a.join('********'));
assertEquals('1,2**********3**********4**********5,6', a.join('**********'));

// Create a cycle.
a.push(a);
assertEquals('1,2345,6', a.join(''));
assertEquals('1,2*3*4*5,6*', a.join('*'));
assertEquals('1,2**3**4**5,6**', a.join('**'));
assertEquals('1,2****3****4****5,6****', a.join('****'));
assertEquals('1,2********3********4********5,6********', a.join('********'));
assertEquals('1,2**********3**********4**********5,6**********', a.join('**********'));

// Replace array.prototype.toString.
var oldToString = Array.prototype.toString;
Array.prototype.toString = function() { return "array"; };
assertEquals('array34arrayarray', a.join(''));
assertEquals('array*3*4*array*array', a.join('*'));
assertEquals('array**3**4**array**array', a.join('**'));
assertEquals('array****3****4****array****array', a.join('****'));
assertEquals('array********3********4********array********array', a.join('********'));
assertEquals('array**********3**********4**********array**********array', a.join('**********'));

Array.prototype.toString = function() { throw 42; };
assertThrows("a.join('')");
assertThrows("a.join('*')");
assertThrows("a.join('**')");
assertThrows("a.join('****')");
assertThrows("a.join('********')");
assertThrows("a.join('**********')");

Array.prototype.toString = function() { return "array"; };
assertEquals('array34arrayarray', a.join(''));
assertEquals('array*3*4*array*array', a.join('*'));
assertEquals('array**3**4**array**array', a.join('**'));
assertEquals('array****3****4****array****array', a.join('****'));
assertEquals('array********3********4********array********array', a.join('********'));
assertEquals('array**********3**********4**********array**********array', a.join('**********'));

// Restore original toString.
delete Array.prototype.toString;
if (Array.prototype.toString != oldToString) {
  Array.prototype.toString = oldToString;
}

var a = new Array(123123);
assertEquals(123122, String(a).length);
assertEquals(123122, a.join(",").length);
assertEquals(246244, a.join("oo").length);

a = new Array(Math.pow(2,32) - 1);  // Max length.
assertEquals("", a.join(""));
a[123123123] = "o";
a[1255215215] = "p";
assertEquals("op", a.join(""));

a = new Array(100001);
for (var i = 0; i < a.length; i++) a[i] = undefined;
a[5] = "ab";
a[90000] = "cd";
assertEquals("abcd", a.join(""));  // Must not throw.


// Make sure that each element is accessed exactly once, and in the correct
// order.
{
  var log = [];
  var p = new Proxy({length: 3, 0: 'a', 1: 'b'}, {
      get: function(t, k, r) { log.push(k); return Reflect.get(t, k, r); }
  });

  assertEquals("a,b,", Array.prototype.join.call(p));
  assertEquals(["length", "0", "1", "2"], log);
}