數組追加

array.push(element1[, ...[, elementN]])
const array = []

array.push(1)
console.log(array) //=> [1]

array.push(2, 3)
console.log(array) //=> [1, 2, 3]
console.log(array.length) //=> 3

首端添加

array.unshift(element1[, ...[, elementN]])
const array = [ 4, 5 ]

array.unshift(3)
console.log(array) //=> [3, 4, 5]

array.unshift(1, 2)
console.log(array) //=> [1, 2, 3, 4, 5]

插入到中間某位置

array.splice(start, deleteCount, element1[, ...[, elementN]])
`第二個參數是刪除若干個元素，設置0為不刪除任何元素`
const array = [ 1, 2, 6, 7 ]

array.splice(2, 0, 3)
console.log(array) //=> [1, 2, 3, 6, 7]

array.splice(3, 0, 4, 5)
console.log(array) //=> [1, 2, 3, 4, 5, 6, 7]

刪除某位置元素

array.splice(start, deleteCount, element1[, ...[, elementN]])
const array = [1, 2, 3, 10, 4, 5]

array.splice(3, 1)

console.log(array) //=> [1, 2, 3, 4, 5]

替換數組某元素

1.
const array = [ 1, 2, 3, 4, 5 ]

array[0] = 10
console.log(array) //=> [10, 2, 3, 4, 5]

2.
const array = [ 1, 2, 3, 4, 5 ]
array.splice(1,1,6)
console.log(array) //=> [ 1, 6, 3, 4, 5 ]

過濾器

array.filter(fn)
const array = [ 1, 2, 3, 4, 5, 6, 7, 8 ]
const evenNumbers = array.filter(function(x) {
  return x % 2 == 0
})

console.log(evenNumbers) //=> [2, 4, 6, 8]

數據轉換

const array = [ 1, 2, 3, 4, 5 ]

const addedArray = array.map(function(x) {
  return x + 2
})

console.log(addedArray) //=> [3,4,5,6,7]

聚合函數

const array = [1,2,3,4]

1.
array.reduce((left,right) => {
  return left + right
})

`針對每次所需要用到的聚合情況做些封裝`
const arrayUtils = {
  function sum(array) {
    return  array.reduce((left,right) => {
      return letf + right
    })
  }

  function multi(array) {
    return array.reduce((left,right) => {
      return left * right
    })
  }
} 

`或者更為抽象的方式，涉及一些函數式編程的概念`
function reduceFn(fn) {
  return function(array) {
    return array.reduce(fn)
  }
}