ES2015 Interview Questions

js-interview.js

// 1
var foo = 2
function bar() {
  if (!foo) {
    var foo = 5
  }
  console.log(foo)
}
bar()

function bar() {
  foo = 666
  console.log(foo)
  function foo() {}
}
bar()

var foo = 0
function bar() {
  if (!foo) {
    let foo = 10
  }
  console.log(foo)
}
bar()

// 2
var myObject = {
    foo: "bar",
    func: function() {
        var self = this
        console.log("outer func:  this.foo = " + this.foo)
        console.log("outer func:  self.foo = " + self.foo)
        (function() {
            console.log("inner func:  this.foo = " + this.foo)
            console.log("inner func:  self.foo = " + self.foo)
        }())
    }
}
myObject.func()

// 3
console.log(0.1 + 0.2)
console.log(0.1 + 0.2 == 0.3)

// 4
(function() {
    console.log(1) 
    setTimeout(() => console.log(2), 1000) 
    setTimeout(() => console.log(3), 0) 
    console.log(4)
})()

// 5
for (var i = 0; i < 5; i++) {
  var btn = document.createElement('button')
  btn.appendChild(document.createTextNode('Button ' + i))
  btn.addEventListener('click', function(){ console.log(i) })
  document.body.appendChild(btn)
}

// 6
console.log("0 || 1 = "+(0 || 1))
console.log("1 || 2 = "+(1 || 2))
console.log("0 && 1 = "+(0 && 1))
console.log("1 && 2 = "+(1 && 2))

// 7
const a={},
    b={key:'b'},
    c={key:'c'}

a[b]=123
a[c]=456

console.log(a[b])

// 8
const hero = {
    _name: 'John Doe',
    getSecretIdentity: function (){
        return this._name
    }
}

const stoleSecretIdentity = hero.getSecretIdentity

console.log(stoleSecretIdentity())
console.log(hero.getSecretIdentity())

// 9
const p3 = new Promise((resolve, reject) => setTimeout(resolve, 100))
const p4 = new Promise((resolve, reject) => setTimeout(reject, 500))

Promise.all([p3, p4]).then(
  () => console.log('success'),
  () => console.log('fail')
)

const p3 = new Promise((resolve, reject) => setTimeout(resolve, 100))
const p4 = new Promise((resolve, reject) => setTimeout(reject, 500))

Promise.race([p3, p4]).then(
  () => console.log('success'),
  () => console.log('fail')
)

// 10
const delay = // ???
Promise.resolve('Adalisk')
  .then(delay(500))
  .then(result => console.log(result)) // "Adalisk"

// 11
const foo = {
  x: 10,
  y: {
    name: 'John'
  }
}
const bar = {
  x: 20,
  ...foo
}
console.log(bar.x)
console.log(foo.y === bar.y)

// 12
const foo = {
  a: 1,
  b: 2,
  c: 3,
  d: 4,
  e: 5
}

// ???
// bar = {
//   c: 3,
//   d: 4,
//   e: 5
// }