JS数组的常用方法-常用篇

  1.join 数组变成字符串      不改变原数组

  let arr1 = ['I', 'Love', 'You']
  console.log(arr1.join(), arr1);//I,Love,You,  ['I', 'Love', 'You']
  console.log(arr1.join('-'), arr1);//I-Love-You  ['I', 'Love', 'You']

  2.split 字符串变成数组     不改变原数组

  let string1 = 'I/Love/You'
  console.log(string1.split('/'), string1); //['I', 'Love', 'You']  'I/Love/You'

  3.push 末尾添加           改变原数组

  4.pop  末尾删除           改变原数组

  5.unshift 首位添加        改变原数组

  6.shift  首位删除         改变原数组

  console.log(arr1.push('ha'),arr1);//4  ['I', 'Love', 'You', 'ha']
  console.log(arr1.pop('ha'),arr1);//ha  ['I', 'Love', 'You']
  console.log(arr1.unshift('ha'),arr1);//4  ['ha', 'I', 'Love', 'You']
  console.log(arr1.shift('ha'),arr1);//ha  ['I', 'Love', 'You']

  7.reverse 反转数组        改变原数组

  console.log(arr1.reverse(), arr1);//["You","Love","I"]   ["You","Love","I"] 

  8.sort 排序               改变原数组

  let arr2 = [3, 9, 2, 90, 34] 
  console.log(arr2, arr2.sort((a, b) => { return a - b }));//[90,34,9,3,2]  [90,34,9,3,2]
  console.log(arr2, arr2.sort((a, b) => { return b - a }));//[2,3,9,34,90]  [2,3,9,34,90]

  9.concat 数组拼接         不会改变原数组

  console.log(arr1.concat(arr2),arr1,arr2);// ['You', 'Love', 'I', 90, 34, 9, 3, 2]  ['You', 'Love', 'I']  [90, 34, 9, 3, 2]

  10.splice 截取/删除替换数组 改变原数组

  11.slice  截取/删除数组     不会改变原数组

  let arr3=[1,2,3,4,5,6,7]
  let arr4=[1,2,3,4,5,6,7]
  let arr5=[1,2,3,4,5,6,7]
  console.log(arr3.splice(0,3),arr3);//[1, 2, 3]  [4, 5, 6, 7]
  console.log(arr4.splice(0,3,'嘿嘿'),arr4);//[1, 2, 3]  ['嘿嘿', 4, 5, 6, 7]
  console.log(arr5.slice(1,3),arr5);//[2, 3]  [1, 2, 3, 4, 5, 6, 7]