# `this` 面试题

# `this` 指向

题目

this.age = 9;
var melon = {
  age: 81,
  get_age: function () {
    return this.age;
  }
};
melon.get_age();   //问题一  
var get_age1 = melon.get_age;
get_age1();        //问题二 
var get_age2 = get_age1.bind(melon);
get_age2();        //问题三

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题目

var x = 10;

function melon() {
  return this.x;
}

let obj = {
  x: 21,
  y: function () {
    return melon();
  },
  z: melon
}

console.log(obj.y());   // 问题一
console.log(obj.z());   // 问题二

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题目

function melon() {
  let arr = [];
  for (var i = 0; i < 3; i++) {
    arr[i] = function () {
      return i;
    }
  }
  return arr;
}
let res = melon();
res.forEach(item => {
  item();		// 问题一
});

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题目

function melon() {
    var res = new Array();
    for(var i = 0; i < 10; i++) {
        res[i] = function() {
            return i;
        }
    }
    return res;
}
var bgg = melon();
bgg[5]();  //问题一
bgg[10];   //问题二

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题目

function Foo() {
    var i = 0;
    return function() {
        console.log(i++);
    }
}

var f1 = Foo(),
    f2 = Foo();
f1();
f1();
f2();

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题目

var bb = 1;
function aa(bb) {
    bb = 2;
    alert(bb);
};
aa(bb);
alert(bb);

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题目

async function async1() {
  console.log('async1 start')
  await async2()
  console.log('async1 end')
}

async function async2() {
  console.log('async2')
}
console.log('script start')
setTimeout(function () {
  console.log('settimeout')
})

async1()
new Promise(function (resolve) {
  console.log('promise1')
  resolve()
}).then(function () {
  console.log('promise2')
})

console.log('script end')

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题目

(async () => {
    console.log(1);
    setTimeout(() => {
        console.log(2);
    }, 0)
    await new Promise((resolve, reject) => {
        console.log(3);
    }).then(() => {
        console.log(4);
    });
    console.log(5);
})();

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题目

for (let i = 0; i <= 2; i++) {
  console.log(i);
  setTimeout(() => {
 	 console.log(i);
  }, 0);
}

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题目

console.log('a');
setTimeout(() => {
	console.log('b');
}, 0);
Promise.resolve().then(() => {
	console.log('c');
}).then(() => {
	console.log('d');
})
console.log('e');

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题目

async function async1() {
  console.log('async1 start');
  await async2();
  console.log('async1 end');
}
async function async2() {
  console.log('async2');
}
console.log('script start');
setTimeout(function () {
  console.log('setTimeout');
}, 0)
async1();
new Promise(function (resolve) {
  console.log('promise1');
  resolve();
}).then(function () {
  console.log('promise2');
});
console.log('script end');

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题目

window.name = 'window';
var person1 = {
  name: 'person1',
  f001: function () {
    console.log(this.name);
  },
  f002: () => console.log(this.name),
  f003: function () {
    return function () {
      console.log(this.name);
    };
  },
  f004: function () {
    return () => {
      console.log(this.name);
    };
  },
};
var person2 = { name: 'person2' };

function fn() {
  return 123;
}

person1.f003()();
person1.f004()();

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# this 面试题

# this 指向

# `this` 面试题

# `this` 指向