Lodash常用用法总结

摘要：是一个轻量级的工具函数库，它方便了日常开发中对数据的操作，提高了开发效率。根据平时开发中对数据的操作，我对常见的用法做了以下总结，方便今后的学习和整理。

Lodash是一个轻量级的JavaScript工具函数库，它方便了日常开发中对数据的操作，提高了开发效率。

​ 日常开发中，通常会对数据，特别是数组和对象进行各种读写等操作：比如去重，拷贝，合并，过滤，求交集，求和等等。根据平时开发中对数据的操作，我对Lodash常见的用法做了以下总结，方便今后的学习和整理。

创建一个数组，元素为0, 1, 2, ... , 23

_.range([start=0], end, [step=1])

let arr = _.range(24)

console.log(arr) // [0, 1, 2, 3, ... , 23]

创建一个数组，元素为100, 100, 100, 100, 100

_.fill(array, value, [start=0], [end=array.length])

let arr = _.fill(Array(5), 100)

console.log(arr) // [100, 100, 100, 100, 100]

获取数组中最后一个元素

_.last(array)

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

console.log(lastElement) // 5

获取数组中倒数第二个元素

_.nth(array, [n=0])

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

console.log(lastSecondElement) // 4

获取对象数组中某一同名属性的属性值集合

_.map(collection, [iteratee=_.identity])

let users = [{
      id: 12,
      name: "Adam",
      hobbies: [
        {name: "running", index: 100},
        {name: "cycling", index: 95}
      ]
   },{
      id: 14,
      name: "Bob",
         hobbies: [
        {name: "movie", index: 98},
        {name: "music", index: 85}
      ]
   },{
      id: 16,
      name: "Charlie",
      hobbies: [
       {name: "travelling", index: 90},
       {name: "fishing", index: 88}
      ]
   },{
      id: 18,
      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) // [12, 14, 16, 18]
console.log(mostFavouriteHobbies) // ["running", "movie", "travelling", "walking"]

获取对象数组中某一属性值最大的对象

_.maxBy(array, [iteratee=_.identity])

let arr = [{a:1, b: 2, c: {d:4}}, {a:3, b: 4, c: {d:6}}]
let maxBObj = _.maxBy(arr, "b")

console.log(maxBObj) // {a: 3, b: 4, c: {d: 6}}

找出两个数组中元素值相同的元素

_.intersection([arrays])

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]

求数值数组中元素值的平均数

_.mean(array)

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

console.log(average) // 3

求对象数组中某个属性值的平均数

_.meanBy(array, [iteratee=_.identity])

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

console.log(average) // 5

获取数组中前n个元素，不改变原数组

_.take(array, [n=1])

let arr = [1, 2, 3, 4, 5]
let part1Arr = _.take(arr, 4)
let part2Arr = _.take(arr, 6)
let part3Arr = _.take([], 5)

console.log(part1Arr) // [1, 2, 3, 4]
console.log(part2Arr) // [1, 2, 3, 4, 5]
console.log(part3Arr) // []

删除数组中值为falsy的元素

_.compact(array)

let arr = [0, 1, false, 2, "", 3, null, undefined, NaN]
let truthyArr = _.compact(arr) 

console.log(truthyArr) // [1, 2, 3]

去重。

_.uniq(array)

let arr = [2, 1, 2, "2", true]
let uniqArr = _.uniq(arr)

console.log(uniqArr) // [2, 1, "2", true]

排序。对象数组，根据对象中的某个属性的值，升序或降序排序

_.orderBy(collection, [iteratees=[_.identity]], [orders])

let users = [
  {user: "Tom", age: 25},
  {user: "Amy", age: 23},
  {user: "Perter", age: 22},
  {user: "Ben", age: 29}
]
let sortedUsers = _.orderBy(users, "age", "desc")

console.log(sortedUsers)
// [{user: "Ben", age: 29}, {user: "Tom", age: 25}, {user: "Amy", age: 23}, {user: "Perter", age: 22}]

分割数组[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]为 [1, 2, 3, 4, 5] 和 [6, 7, 8, 9, 10]

_.chunk(array, [size=1])

let arr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
let [left, right] = _.chunk(arr, 5)

console.log(left) // [1, 2, 3, 4, 5]
console.log(right) // [6, 7, 8, 9, 10]

脱掉一层[]

_.flatten(array)

let address = {
  "江苏省": ["南京市", "苏州市"],
  "浙江省": ["杭州市", "绍兴市"]
}
let cities = _.flatten(_.values(address))

console.log(cities) // ["南京市", "苏州市", "杭州市", "绍兴市"]

将多维数组转为一维数组

_.flattenDeep(array)

let flattenedArr = _.flattenDeep([1, [2, [3, [4]], 5]]);

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

通过数组["x", "y"] 和 数组[10, 10] 创建对象 {x: 10, y: 10}

_.zipObject([props=[]], [values=[]])

let keys = ["x", "y"]
let values = [10, 10]
let obj = _.zipObject(keys, values) 

console.log(obj) // {x: 10, y: 10}

合并对象

_.assign(object, [sources])

let desObj = {name: "", gender: "male", job: "developer"}
let sourceObj = {name: "Tom", job: ""}
let mergedObj = _.assign(desObj, sourceObj)

console.log(mergedObj) // {name: "Tom", gender: "male", job: ""}

深拷贝对象

_.cloneDeep(value)

let sourceObj = {department_id: 1, permissions: {management: [1, 2, 3, 4], store: [11, 12, 13, 14]}}
let desObj = _.cloneDeep(sourceObj)
desObj.permissions.store.push(15, 16)

console.log(desObj)
// {department_id: 1, permissions: {management: [1, 2, 3, 4], store: [11, 12, 13, 14, 15, 16]}}
console.log(sourceObj)
// {department_id: 1, permissions: {management: [1, 2, 3, 4], store: [11, 12, 13, 14]}}

合并多个对象中key值相同的键值对

_.merge(object, [sources])

let obj1 = {"9": {name: "乐购超市"}}
let obj2 = {"9": {storeToken: "xxx"}}
let obj3 = {"9": {storePosition: "Hangzhou"}}
let mergedObj = _.merge(obj1, obj2, obj3) 

console.log(mergedObj)
// 9: {name: "乐购超市", storeToken: "xxx", storePosition: "Hangzhou"}

判断对象中是否有某个属性

_.has(object, path)

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

console.log(hasC) // true

获取对象中的某个属性的值

_.get(object, path, [defaultValue])

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

console.log(c) // 3

设置对象中的某个属性的值

_.set(object, path, value)

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

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

对多个对象相同属性的属性值求和。

let customers = {
  new_customer: {0: 33, 1: 5, ... , 23: 0},
  old_customer: {0: 22, 1: 7, ... , 24: 0}
}
let customer = {}
let keys = _.keys(customers.new_customer)
let values = _.values(customers)
_.map(keys, key => {
  customer[key] = _.sumBy(values, key)
})

customers.customer = customer

console.log(customers)
// console
{
    customer: {0: 55, 1: 12, ... , 23: 0}
  new_customer: {0: 33, 1: 5, ... , 23: 0}
  old_customer: {0: 22, 1: 7, ... , 23: 0}
}

生成一个随机数，范围n~m

_.random([lower=0], [upper=1], [floating])

let random1 = _.random(2, 5)
let random2 = _.random(5)

console.log(random1) // 2, 3, 4, 5
console.log(random2) // 0, 1, 2, 3, 4, 5

判断数据类型

_.isNumber(value)
_.isInteger(value)
...
_.isPlainObject(value)

let variable = "hello";
// Number
console.log(_.isNumber(variable));
// Integer
console.log(_.isInteger(variable));
// Boolean
console.log(_.isBoolean(variable));
// String
console.log(_.isString(variable));
// Null
console.log(_.isNull(variable));
// Undefined
console.log(_.isUndefined(variable));
// Array
console.log(_.isArray(variable));
// Function
console.log(_.isFunction(variable));
// Object
console.log(_.isPlainObject(variable));
// Date
console.log(_.isDate(variable));

// DOM element
console.log(_.isElement(variable));

数据类型转换

_.toArray

_.toArray("abc") // ["a", "b", "c"]

_.toInteger

_.toInteger(3.2); // 3
_.toInteger("3.2"); // 3

_.toNumber

_.toNumber("3.2") // 3.2

_.toString

_.toString(1); // "1"
_.toString([1, 2, 3]); // "1,2,3"

重复多次某个元素

_.times(n, [iteratee=_.identity])

const dateParams = _.times(2, () => "2018-08-27");
console.log(dateParams) // ["2018-08-27", "2018-08-27"]