// Copyright 2014 the V8 project authors. All rights reserved. // Use of this source code is governed by a BSD-style license that can be // found in the LICENSE file. // Note: concat does not currently support species so there is no difference // between [].concat(foo) and Array.prototype.concat.apply(foo). var log = []; var logger = {}; var handler = new Proxy({}, logger); logger.get = function(t, trap, r) { return function(...args) { log.push([trap, ...args]); return Reflect[trap](...args); } }; var target = ["a", "b"]; target[Symbol.isConcatSpreadable] = undefined; var obj = new Proxy(target, handler); log.length = 0; assertEquals(["a", "b"], [].concat(obj)); assertEquals(6, log.length); for (var i in log) assertSame(target, log[i][1]); assertEquals(["get", target, Symbol.isConcatSpreadable, obj], log[0]); assertEquals(["get", target, "length", obj], log[1]); assertEquals(["has", target, "0"], log[2]); assertEquals(["get", target, "0", obj], log[3]); assertEquals(["has", target, "1"], log[4]); assertEquals(["get", target, "1", obj], log[5]); log.length = 0; assertEquals(["a", "b"], Array.prototype.concat.apply(obj)); assertEquals(7, log.length); for (var i in log) assertSame(target, log[i][1]); assertEquals(["get", target, "constructor", obj], log[0]); assertEquals(["get", target, Symbol.isConcatSpreadable, obj], log[1]); assertEquals(["get", target, "length", obj], log[2]); assertEquals(["has", target, "0"], log[3]); assertEquals(["get", target, "0", obj], log[4]); assertEquals(["has", target, "1"], log[5]); assertEquals(["get", target, "1", obj], log[6]);