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layout: post title: ECMAScript 6 六级考试 modified: 2017-08-25 tags: [javascript] image: feature: abstract-3.jpg credit: dargadgetz creditlink: http://www.dargadgetz.com/ios-7-abstract-wallpaper-pack-for-iphone-5-and-ipod-touch-retina/ comments: true

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这份试卷我并没有准备答案，一方面所有的代码可以立即在浏览器中执行看到（我）效（很）果（懒）；另一方面这也并非是一场真的（我）考（很）试（懒），而是用于检测自己ES6知识并且查漏补缺，所以不必有太大压力。

这份试卷的内容主要来源于两份我学习ES6的资料：nzakas（JavaScript高级程序设计的作者）的开源图书understandinges6，以及Nicolás Bevacqua的ES6 in Depth系列。如果你对文中的一些问题有疑惑，你一定可以从它们中找到答案。

一共44道题，7道选择题，8道问答题，29道代码执行题。这些题目当然不会是省油的灯，我尽量挑选模棱两可，让人疑惑又或者容易疏忽的知识点

这份试卷难免会有纰漏或者不严谨的地方，比如没有正确答案或者答案不唯一，如果有出现这样的情况，请留言给我让我及时纠正。

最后，如果你有兴趣的话可以把你认为的正确答案或者解释写在留言中供大家参考

选择题（有一个或多个答案）

请说出以下每一段代码的执行结果，或者是否会报错

if (true) {
    console.log(temp);
    console.log(typeof temp);
    const temp = 1;
}

let message = `Multiline
                   string`;
console.log(message)

[1, 2, 3].map(n => { number: n })

function mixArgs(first, second = "b") {
    console.log(arguments.length);
    console.log(first === arguments[0]);
    console.log(second === arguments[1]);
}
mixArgs();

const a = { b: 'c'}
Object.defineProperty(a, 'visible', { enumerable: false, value: 'boo! ahhh!' })
Object.assign({}, a);

var a = [[1], [2], [3]];
var b = [...a];
b.shift().shift();
console.log(a);

let obj1 = { a: 0 , b: { c: 0}};
let obj2 = Object.assign({}, obj1);
obj1.b.c = 2;
console.log(JSON.stringify(obj2))

const x = { a: { a: 1 } };
const y = { a: { b: 1 } };
const z = { ...x, ...y };
console.log(z);

var obj = {
    a: 1,
    0: 1,
    c: 1,
    2: 1,
    b: 1,
    1: 1
};
obj.d = 1;
console.log(Object.getOwnPropertyNames(obj).join(""));

let node = {
        type: "Identifier"
    };
let { type: localType = 'foo', name: localName = 'bar' } = node;

console.log(localType);
console.log(localName);

let node = {
        type: "Identifier",
        name: "foo"
    },
    type = "Literal",
    name = 5;
({ type, name } = node);
console.log(type); 
console.log(name);

let a = 1,
    b = 2;

[ a, b ] = [ b, a ];

console.log(a);
console.log(b);

var {foo=3} = { foo: 2 }
console.log(foo)

var {foo=3} = { foo: undefined }
console.log(foo)

var {foo=3} = { bar: 2 }
console.log(foo)

var [b=10] = [undefined]
console.log(b)

let uid3 = Symbol("uid");
console.log(Symbol.keyFor(uid3));

function MyObject() {
    // ...
}

Object.defineProperty(MyObject, Symbol.hasInstance, {
    value: function(v) {
        return false;
    }
});

let obj = new MyObject();
console.log(obj instanceof MyObject);

let set = new Set([1, 2, 3, 4, 5, 5, 5, 5]);
console.log(set.size);

var map = new Map()
map.set('a', 'a')
map.set('a', 'b')
map.set('a', 'c')
console.log([...map])

var map = new Map([[NaN, 1], [Symbol(), 2], ['foo', 'bar']])
console.log(map.has(NaN))
console.log(map.has(Symbol()))

var sym = Symbol()
var map = new Map([[NaN, 1], [sym, 2], ['foo', 'bar']])
console.log(map.has(sym))

function* generator () {
  yield 'p'
  console.log('o')
  yield 'n'
  console.log('y')
  yield 'f'
  console.log('o')
  yield 'o'
  console.log('!')
}

var foo = generator()
for (let pony of foo) {
  console.log(pony)
}

var foo = generator()
console.log([...foo])

function *gen() {
    yield 5 + 2;
}
const g = gen();
g.next()

function *createIterator() {
    let first = yield 1;
    let second = yield first + 2;  
    yield second + 3;                   
}

let iterator = createIterator();

console.log(iterator.next());
console.log(iterator.next(4));
console.log(iterator.next(5));
console.log(iterator.next());

function *createIterator() {
    yield 1;
    return;
    yield 2;
    yield 3;
}

let iterator = createIterator();

console.log(iterator.next());
console.log(iterator.next());

let PersonClass = class PersonClass2 {
  //...
};

console.log(typeof PersonClass)
console.log(typeof PersonClass2)

let propertyName = 'sayHi';
class Test {
    [propertyName]() {
        console.log('Hello World');
    }
}
const test = new Test();
test.sayHi();
test[propertyName]();

propertyName = 'sayBye';
const test2 = new Test();

test.sayHi();
test[propertyName]();

let promise = new Promise(function(resolve, reject) {
    console.log("Promise");
    resolve();
});

promise.then(function() {
    console.log("Resolved.");
});

console.log("Hi!");

let p1 = new Promise(function(resolve, reject) {
    resolve(42);
});

let p2 = new Promise(function(resolve, reject) {
    resolve(43);
});

p1.then(function(value) {
    console.log(value);
    return p2;
}).then(function(value) {
    console.log(value);
});

// example.js:
export var name = "Nicholas";
export function setName(newName) {
    name = newName;
}

// another_example.js:
import { name, setName } from "./example.js";

console.log(name);
setName("Greg");
console.log(name);

let target = {
    name: "target"
};
let { proxy, revoke } = Proxy.revocable(target, {});

console.log(proxy.name);
revoke();
console.log(proxy.name);

let ints = new Int16Array([25, 50]);

console.log(ints.length);
console.log(ints[0]); 
console.log(ints[1]); 

ints[2] = 5;

console.log(ints.length);
console.log(ints[2]);

问答题