JS语法_基础回顾

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JS语法_基础回顾

二建零基础备考指导课

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标签：onsconsole字符串拼接i++pre回顾logstr1start

数组方法

push

// log
Array.prototype.$push = function () {
  for (let i = 0; i < arguments.length; i++) {
    this[this.length] = arguments[i]
  }
  return this.length
}
let arr = [1, 2]
console.log(arr.$push(3, 4))
console.log(arr)

join

// log
let str1 = ‘1‘
let str2 = ‘2‘
let str3 = ‘3‘
let str4 = ‘4‘
let str5 = ‘5‘
let str6 = ‘6‘
let arr = [str1, str2, str3, str4, str5, str6]
let strFinal = ‘‘

function f1() {
  for (let i = 0; i < arr.length; i++) {
    strFinal += arr[i]
  }
}

function f2() {
  strFinal += arr.join(‘‘)
}

{
  let start = new Date().getTime()
  for (let i = 0; i < 100000; i++) {
    f1()
  }
  let end = new Date().getTime()
  console.log(‘字符串拼接耗时: ‘ + (end - start))
}

{
  let start = new Date().getTime()
  for (let i = 0; i < 10000; i++) {
    f2()
  }
  let end = new Date().getTime()
  console.log(‘join耗时: ‘ + (end - start))
}

类数组

// log
let obj = {
  1: ‘a‘,
  2: ‘b‘,
  3: ‘c‘,
  length: 3,
  push: Array.prototype.push
}
obj.push(‘d‘)
console.log(obj)

JS语法_基础回顾

标签：onsconsole字符串拼接i++pre回顾logstr1start

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