object-class-tostring.js

Enable keyboard shortcuts

function testCongruent(i) {

  var p = {};

  var o = {

    // Add toString as an own property, so it'll be always found on this object,

    // even when properties are changed on the prototype.

    toString: Object.prototype.toString,

    // Add a custom prototype, so we can add @@toStringTag without modifying the

    // shape of this object.

    __proto__: p,

};

  var xs = [{}, p];

  var ys = ["[object Object]", "[object Test]"];

  for (var j = 0; j <= 100; ++j) {

    // Don't use if-statements to avoid cold code bailouts

    var x = xs[(i === 1 && j === 100)|0];

    var y = ys[(i === 1 && j === 100)|0];

    // |o.toString()| must be executed twice, because |x[Symbol.toStringTag]| may

    // have modified |o|.

    var r = o.toString();

    x[Symbol.toStringTag] = "Test";

    var e = o.toString();

    assertEq(r, "[object Object]");

    assertEq(e, y);

for (var i = 0; i < 2; ++i) testCongruent(i);

function testUnobserved(i) {

  var p = {};

  var o = {

    // Add toString as an own property, so it'll be always found on this object,

    // even when properties are changed on the prototype.

    toString: Object.prototype.toString,

    // Add a custom prototype, so we can add @@toStringTag without modifying the

    // shape of this object.

    __proto__: p,

};

  var xs = [{}, p];

  var ys = [false, true];

  for (var j = 0; j <= 100; ++j) {

    // Don't use if-statements to avoid cold code bailouts

    var x = xs[(i === 1 && j === 100)|0];

    var y = ys[(i === 1 && j === 100)|0];

    var executed = false;

    Object.defineProperty(x, Symbol.toStringTag, {

      configurable: true,

      get() {

        executed = true;

});

    // |o.toString()| must be executed even when the result isn't observed.

    o.toString();

    assertEq(executed, y);

for (var i = 0; i < 2; ++i) testUnobserved(i);