JSTests/test262/test/language/expressions/object/computed-property-evaluation-order.js

// Copyright (C) 2016 Michael Ficarra. All rights reserved.
// This code is governed by the BSD license found in the LICENSE file.
/*---
esid: sec-object-initializer-runtime-semantics-propertydefinitionevaluation
description: >
    Evaluation of PropertyDefinitionList occurs in order, and each
    PropertyDefinition's PropertyName is evaluated before its
    AssignmentExpression.
---*/

var counter = 0;
var o = {
  [++counter]: ++counter,
  [++counter]: ++counter,
  [++counter]: ++counter,
}

var keys = Object.keys(o);

assert.sameValue(keys.length, 3, '3 PropertyDefinitions should result in 3 properties');
assert.sameValue(keys[0], '1');
assert.sameValue(o[keys[0]], 2);
assert.sameValue(keys[1], '3');
assert.sameValue(o[keys[1]], 4);
assert.sameValue(keys[2], '5');
assert.sameValue(o[keys[2]], 6);