在開發中，數組的使用場景非常多，平日中也涉及到很多數組相關操作。本篇文章就歸納總結了一些常見的操作方法分享給大家，如果在開發中能信手拈來，可大大提高開發效率。
1、產生隨機數字
遍歷數組，每次循環都隨機一個在數組長度範圍內的數，並交換本次循環的位置和隨機數位置上的元素
function randomSort1(arr) {
for (let i = 0, l = arr.length; i < l; i++) {
let rc = parseInt(Math.random() * l)
// 让当前循环的数组元素和随机出来的数组元素交换位置
const empty = arr[i]
arr[i] = arr[rc]
arr[rc] = empty
}
return arr
}
var arr1 = [1, 2, 3, 4, 5, 6, 7, 8, 9]
// 下面两次的结果肯定是不一样的；
console.log(randomSort1(arr1))
console.log(randomSort1(arr1))#2、產生新數組
function randomSort2(arr) {
var mixedArr = []
while (arr.length > 0) {
let rc = parseInt(Math.random() * arr.length)
mixedArr.push(arr[rc])
arr.splice(rc, 1)
}
return mixedArr
}
// 例子
var arr1 = [1, 2, 3, 4, 5, 6, 7, 8, 9]
console.log(randomSort2(arr1))#3、 arr.sort
##
function randomSort3(arr) {
arr.sort(function (a, b) {
return Math.random() - 0.5
})
return arr
}
// 例子
var arr1 = [1, 2, 3, 4, 5, 6, 7, 8, 9]
console.log(randomSort3(arr1))function compare(property) {
return function (a, b) {
let value1 = a[property]
let value2 = b[property]
return value1 - value2
}
}
let arr = [
{ name: 'zopp', age: 10 },
{ name: 'gpp', age: 18 },
{ name: 'yjj', age: 8 },
]
console.log(arr.sort(compare('age')))
2、多個屬性排序
function by(name, minor) {
return function(o, p) {
let a, b
if (o && p && typeof o === 'object' && typeof p === 'object') {
a = o[name]
b = p[name]
if (a === b) {
return typeof minor === 'function' ? minor(o, p) : 0
}
if (typeof a === typeof b) {
return a < b ? -1 : 1
}
return typeof a < typeof b ? -1 : 1
} else {
thro('error')
}
}
},ary = arr.flat(Infinity)
console.log([1, [2, 3, [4, 5, [6, 7]]]].flat(Infinity))
2、普通遞歸
let result = []
let flatten = function (arr) {
for (let i = 0; i < arr.length; i++) {
let item = arr[i]
if (Array.isArray(arr[i])) {
flatten(item)
} else {
result.push(item)
}
}
return result
}
let arr = [1, 2, [3, 4], [5, [6, 7]]]
console.log(flatten(arr))function flatten(arr) {
return arr.reduce((pre, cur) => {
return pre.concat(Array.isArray(cur) ? flatten(cur) : cur)
}, [])
}
let arr = [1, 2, [3, 4], [5, [6, 7]]]
console.log(flatten(arr))#
function flatten(arr) {
while (arr.some((item) => Array.isArray(item))) {
arr = [].concat(...arr)
}
return arr
}
let arr = [1, 2, [3, 4], [5, [6, 7]]]
console.log(flatten(arr))function unique(arr) {
var newArr = []
for (var i = 0; i < arr.length; i++) {
if (newArr.indexOf(arr[i]) === -1) {
newArr.push(arr[i])
}
}
return newArr
}
console.log(unique([1, 1, 2, 3, 5, 3, 1, 5, 6, 7, 4]))
2、先將原數組排序，在與相鄰的進行比較，如果不同則存入新數組。
function unique(arr) {
var formArr = arr.sort()
var newArr = [formArr[0]]
for (let i = 1; i < formArr.length; i++) {
if (formArr[i] !== formArr[i - 1]) {
newArr.push(formArr[i])
}
}
return newArr
}
console.log(unique([1, 1, 2, 3, 5, 3, 1, 5, 6, 7, 4]))function unique(arr) {
var obj = {}
var newArr = []
for (let i = 0; i < arr.length; i++) {
if (!obj[arr[i]]) {
obj[arr[i]] = 1
newArr.push(arr[i])
}
}
return newArr
}
console.log(unique([1, 1, 2, 3, 5, 3, 1, 5, 6, 7, 4]))function unique(arr) {
var newArr = []
for (var i = 0; i < arr.length; i++) {
if (!newArr.includes(arr[i])) {
newArr.push(arr[i])
}
}
return newArr
}
console.log(unique([1, 1, 2, 3, 5, 3, 1, 5, 6, 7, 4]))function unique(arr) {
var newArr = []
newArr = arr.filter(function (item) {
return newArr.includes(item) ? '' : newArr.push(item)
})
return newArr
}
console.log(unique([1, 1, 2, 3, 5, 3, 1, 5, 6, 7, 4]))function unique(arr) {
return Array.from(new Set(arr)) // 利用Array.from将Set结构转换成数组
}
console.log(unique([1, 1, 2, 3, 5, 3, 1, 5, 6, 7, 4]))function unique(arr) {
const res = new Map()
return arr.filter((item) => !res.has(item.productName) && res.set(item.productName, 1))
}
方法二
function unique(arr) {
let result = {}
let obj = {}
for (var i = 0; i < arr.length; i++) {
if (!obj[arr[i].key]) {
result.push(arr[i])
obj[arr[i].key] = true
}
}
}# # 實作方法 javascript學習教學 以上是【歸納總結】JS數組常見的操作方法，幫助你提升開發效率！的詳細內容。更多資訊請關注PHP中文網其他相關文章！let a = [1, 2, 3]
let b = [2, 4, 5]
// 并集
let union = a.concat(b.filter((v) => !a.includes(v)))
// [1,2,3,4,5]
// 交集
let intersection = a.filter((v) => b.includes(v))
// [2]
// 差集
let difference = a.concat(b).filter((v) => !a.includes(v) || !b.includes(v))
// [1,3,4,5]
2、ES6 的Set 資料結構
let a = new Set([1, 2, 3])
let b = new Set([2, 4, 5])
// 并集
let union = new Set([...a, ...b])
// Set {1, 2, 3, 4,5}
// 交集
let intersect = new Set([...a].filter((x) => b.has(x)))
// set {2}
// a 相对于 b 的）差集
let difference = new Set([...a].filter((x) => !b.has(x)))
// Set {1, 3}#1、萬能的for 迴圈
function sum(arr) {
var s = 0
for (var i = arr.length - 1; i >= 0; i--) {
s += arr[i]
}
return s
}
sum([1, 2, 3, 4, 5]) // 15
2、遞歸方法function sum(arr) {
var len = arr.length
if (len == 0) {
return 0
} else if (len == 1) {
return arr[0]
} else {
return arr[0] + sum(arr.slice(1))
}
}
sum([1, 2, 3, 4, 5]) // 15function sum(arr) {
return arr.reduce(function (prev, curr) {
return prev + curr
}, 0)
}
sum([1, 2, 3, 4, 5]) // 151、Array 的slice 方法
let arr = Array.prototype.slice.call(arguments)
2、ES6 的Array.from()let arr = Array.from(arguments)
<div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">let arr = [...arguments]</pre><div class="contentsignin">登入後複製</div></div>陣列上下移動
陣列轉換為樹狀結構function swapItems(arr, index1, index2) {
arr[index1] = arr.splice(index2, 1, arr[index1])[0]
return arr
}
function up(arr, index) {
if (index === 0) {
return
}
this.swapItems(arr, index, index - 1)
}
function down(arr, index) {
if (index === this.list.length - 1) {
return
}
this.swapItems(arr, index, index + 1)
}
#將下列資料轉換為樹狀結構
let arr = [
{
id: 1,
name: '1',
pid: 0,
},
{
id: 2,
name: '1-1',
pid: 1,
},
{
id: 3,
name: '1-1-1',
pid: 2,
},
{
id: 4,
name: '1-2',
pid: 1,
},
{
id: 5,
name: '1-2-2',
pid: 4,
},
{
id: 6,
name: '1-1-1-1',
pid: 3,
},
{
id: 7,
name: '2',
},
]function toTree(data, parentId = 0) {
var itemArr = []
for (var i = 0; i < data.length; i++) {
var node = data[i]
if (node.pid === parentId) {
var newNode = {
...node,
name: node.name,
id: node.id,
children: toTree(data, node.id),
}
itemArr.push(newNode)
}
}
return itemArr
}
console.log(toTree(arr))
