前端工具库lodash里的常用方法

last

获取数组中最后一个元素

let arr = [1, 2, 3, 4, 5]
let last = _.last(arr) 

console.log(last ) // 5

nth

获取数组中倒数第几个元素

let arr = [1, 2, 3, 4, 5]
let lastSecond = _.nth(-2) 

console.log(lastSecond ) // 4

map

获取对象数组中某一同名属性的属性值集合,第一个参数是对象，第二个参数属性名

let users = [{
      id: 1,
      name: 'mickey',
      hobbies: [
        {name: 'running', index: 100},
        {name: 'cycling', index: 95}
      ]
   },{
      id: 2,
      name: 'jack',
      hobbies: [
        {name: 'movie', index: 98},
        {name: 'music', index: 85}
      ]
   },{
      id: 3,
      name: 'Bob',
      hobbies: [
       {name: 'travelling', index: 90},
       {name: 'fishing', index: 88}
      ]
   },{
      id: 4,
      name: 'David',
      hobbies: [
       {name: 'walking', index: 99},
       {name: 'football', index: 85}
     ]                


   }
]

let userIds = _.map(users, 'id')
let mostFavouriteHobbies = _.map(users, 'hobbies[0].name')

console.log(userIds) // [1, 2, 3, 4]
console.log(mostFavouriteHobbies) // ["running", "movie", "travelling", "walking"]

intersection

找出两个数组中元素值相同的元素

let arr1 = [2, 1, {a: 1, b: 2}]
let arr2 = [2, 3, {a: 1, b: 2}]
let intersection = _.intersection(arr1, arr2) 

console.log(intersection) // [2]

mean

求数值数组中元素值的平均数

let numbers = [1, 2, 3, 4, 5]
let average = _.mean(numbers)

console.log(average) // 3

menaBy

求对象数组中某个属性值的平均数

let objects = [{ 'n': 4 }, { 'n': 2 }, { 'n': 8 }, { 'n': 6 }]
let average = _.meanBy(objects, 'n')

console.log(average) // 5

unid、uniqBy

数组去重和数组中的对象去重

//普通的数据去重
let arrA = [1,1,2,2,3,4,5]

console.log(arrA.unid(arrA)) // [1,2,3,4,5]

//数组中对象得去重

let arrB = [{name:mickey},{name:mickey},{age:25}]

console.log(arrB.uniqBy(arrB,"name"))  // [{name:mickey},{age:25}a]

cloneDeep

clone数据，类似于深拷贝。

let obj = [{loadsh:1},2,3,4]
let cloneObj = clone(obj)
console.log(cloneObj) // [{loadsh:1},2,3,4]
obj[0].loadsh = 3
console.log(cloneObj) // [{loadsh:3},2,3,4]
//clone拷贝的数据是浅拷贝

let obj = [{loadsh:1},2,3,4]
let cloneObj = cloneDeep(obj)
console.log(cloneObj) // [{loadsh:1},2,3,4]
obj[0].loadsh = 3
console.log(cloneObj) // [{loadsh:1},2,3,4]

//cloneDeep拷贝的数据是深拷贝

truncate

该函数可以截断string字符串，如果字符串超出了限定的最大值，那么就会截断字符串，并且用omission替代，默认的omission为'...'。 结合ToolTip，可以在展示数据时很方便的处理数据。

get

获取对象中的某个属性的值

let obj = {a: [{b: {c: 3}}]}
let c = _.get(obj, 'a[0].b.c')

console.log(c) // 3

has

判断对象中是否有某个属性

let obj = {a: [{b: {c: 3}}]}
let hasC = _.has(obj, 'a[0].b.c')

console.log(hasC) // true

set

设置对象中的某个值

let obj = {a: [{b: {c: 3}}]}
let newObj = _.set(obj, 'a[0].b.c', 4);

console.log(obj.a[0].b.c); // 4