快手面试题(day6)

[robbiemie]

Q1:

var name = '123'
var obj = {
    name: "456",
    getName: function() {
        function printName() {
            console.log(this, this.name) // this->window:123
        }
        printName()
    }
}

obj.getName()

Q2:

var a = 1

function fn() {
    console.log(a)
    var a = 2 // undefined
    // 如果是这个： let a = 2 throw error
}

fn()

Q3:

setTimeout(() => {
  console.log('1') // 宏
}, 0)

new Promise((resolve, reject) => {
  console.log('2') // 同
  process.nextTick(resolve)
}).then(_ => {
  console.log('3') // 微
})

process.nextTick(() => {
  console.log('4') // 微
})

setImmediate(() => {
  console.log(5) // 宏
})

Q4:

/**
 * 实现 repeat 函数
 * @param {Function} 执行函数
 * @param {number} 执行次数
 * @param {number} 执行间隔
 */
const repeatFunc = repeat(console.log, 4, 1000)

repeatFunc('hello')

Q5:

let arr = [
    {a: 1, b: 2},
    {b: 2, a: 1},
    {a:'1', b:2}
]

/**
 * 去重
 * 要求: 时间复杂度尽量最低
*/ 
const newArr = filters(arr)
/**
newArr = [
    {a: 1, b: 2},
    {a:'1', b:2}
]
 */

Q6:

// 实现一个 EventEmit 类
class EventEmit {
    on() {}
    once() {}
    off() {}
    emit() {}
}

[robbiemie]

/**
 * 实现 repeat 函数
 * @param {Function} 执行函数
 * @param {number} 执行次数
 * @param {number} 执行间隔
 */
const repeatFunc = repeat(console.log, 4, 1000)

repeatFunc('hello')




/**
 * 实现 repeat 函数
 * @param {Function} 执行函数
 * @param {number} 执行次数
 * @param {number} 执行间隔
 */
function repeat(handler, count, wait) {
  let remain = count
  const repeatFunction = function(...args) {
    if(remain === 0) return
    const arg = args[0]
    if(wait === 0) {
      // 立即执行
      handler(arg)
      remain--;
    } else {
      // 间隔执行
      handler.id = setTimeout(() => {
        clearTimeout(handler.id)
        handler(arg)
        remain--
        if(remain>0) {
          repeatFunc(arg)
        }
      }, wait)
    }
  }

  return repeatFunction
}


const repeatFunc = repeat(console.log, 4, 1000)

repeatFunc('hello')

[robbiemie]

let arr = [
    {a: 1, b: 2},
    {b: 2, a: 1},
    {a:'1', b:2}
]

/**
 * 去重
 * 要求: 时间复杂度尽量最低
*/ 
const newArr = filters(arr)
/**
newArr = [
    {a: 1, b: 2},
    {a:'1', b:2}
]
 */


let arr = [
  {a: 1, b: 2},
  {b: 2, a: 1},
  {a:'1', b:2}
]

function filters(arr) {
  const list = arr.slice()
  let set = new Set()
  for(let item of list) {
    set.add(JSON.stringify({
      a: item['a'],
      b: item['b']
    }))
  }

  return [...set].map(item => JSON.parse(item));
}

/**
* 去重
* 要求: 时间复杂度尽量最低
*/
const newArr = filters(arr)
console.log(newArr)
/**
newArr = [
  {a: 1, b: 2},
  {a:'1', b:2}
]
*/

[robbiemie]

// 实现一个 EventEmit 类
class EventEmit {
    on() {}
    once() {}
    off() {}
    emit() {}
}


// 实现一个 EventEmit 类
class EventEmit {
  constructor() {
    this.eventMap = {}
  }
  on(name, handler) {
    if(Array.isArray(this.eventMap[name]))  this.eventMap[name] = []
    if(typeof handler === 'function') {
      this.eventMap[name].push(handler)
    }
  }
  once(name, handler) {
    if(Array.isArray(this.eventMap[name]))  this.eventMap[name] = []
    handler.once = true
    if(typeof handler === 'function') {
      this.eventMap[name].push(handler)
    }
  }
  off(name, handler) {
    if(Array.isArray(this.eventMap[name]))  this.eventMap[name] = []
    const queue = this.eventMap[name];
    const index = queue.findIndex(item => item === handler);
    queue.splice(index, 1);
    this.eventMap[name] = queue
  }
  emit(name, ...args) {
    if(Array.isArray(this.eventMap[name]))  this.eventMap[name] = []
    const queue = this.eventMap[name];
    for(let handler of queue) {
      if(typeof handler === 'function') {
        handler(args)
      }
      if(handler.once) {
        handler = null
      }
    }
    this.eventMap[name] = queue.filter(item => item)
  }
}

[robbiemie]

// linkNode
// [1,2,3]
// [2,4,5]

// [1,2,2,3,4,5]

/**
 * LinkNode
 * @param {number | null} value 
 * @param {LinkNode | null} next
 */

/**
 * 
 * @param {LinkNode} link1 
 * @param {LinkNode} link2 
 */
 function merge(link1, link2) {
    let point = new LinkNode(0)
    let link = point
    // 遍历两个链表
    while(link1 || link2) {
        if(link1 && link2) {
            if(link1.value < link2.value) {
                point.next = link1
                link1 = link1.next
            } else {
                point.next = link2
                link2 = link2.next
            }
            point = point.next
        } else if(link1) {
            // link2 === null
            point.next = link1
            point = point.next
            link1 = link1.next
        } else {
            // link1 === null
            point.next = link2
            point = point.next
            link2 = link2.next
        }
    }
    return link.next
}


merge([], [])