摘要：是一個輕量級的工具函數(shù)庫，它方便了日常開發(fā)中對數(shù)據(jù)的操作，提高了開發(fā)效率。根據(jù)平時開發(fā)中對數(shù)據(jù)的操作，我對常見的用法做了以下總結(jié)，方便今后的學(xué)習(xí)和整理。

Lodash是一個輕量級的JavaScript工具函數(shù)庫，它方便了日常開發(fā)中對數(shù)據(jù)的操作，提高了開發(fā)效率。

? 日常開發(fā)中，通常會對數(shù)據(jù)，特別是數(shù)組和對象進(jìn)行各種讀寫等操作：比如去重，拷貝，合并，過濾，求交集，求和等等。根據(jù)平時開發(fā)中對數(shù)據(jù)的操作，我對Lodash常見的用法做了以下總結(jié)，方便今后的學(xué)習(xí)和整理。

創(chuàng)建一個數(shù)組，元素為0, 1, 2, ... , 23

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

let arr = _.range(24)

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

創(chuàng)建一個數(shù)組，元素為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]

獲取數(shù)組中最后一個元素

_.last(array)

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

console.log(lastElement) // 5

獲取數(shù)組中倒數(shù)第二個元素

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

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

console.log(lastSecondElement) // 4

獲取對象數(shù)組中某一同名屬性的屬性值集合

_.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"]

獲取對象數(shù)組中某一屬性值最大的對象

_.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}}

找出兩個數(shù)組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]

求數(shù)值數(shù)組中元素值的平均數(shù)

_.mean(array)

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

console.log(average) // 3

求對象數(shù)組中某個屬性值的平均數(shù)

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

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

console.log(average) // 5

獲取數(shù)組中前n個元素，不改變原數(shù)組

_.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) // []

刪除數(shù)組中值為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。對象數(shù)組，根據(jù)對象中的某個屬性的值，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}]

分割數(shù)組[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]為 [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]

脫掉一層[]

_.flatten(array)

let address = {
  "江蘇省": ["南京市", "蘇州市"],
  "浙江省": ["杭州市", "紹興市"]
}
let cities = _.flatten(_.values(address))

console.log(cities) // ["南京市", "蘇州市", "杭州市", "紹興市"]

將多維數(shù)組轉(zhuǎn)為一維數(shù)組

_.flattenDeep(array)

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

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

通過數(shù)組["x", "y"] 和 數(shù)組[10, 10] 創(chuàng)建對象 {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}

合并對象

_.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: ""}

深拷貝對象

_.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]}}

合并多個對象中key值相同的鍵值對

_.merge(object, [sources])

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

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

判斷對象中是否有某個屬性

_.has(object, path)

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

console.log(hasC) // true

獲取對象中的某個屬性的值

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

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

console.log(c) // 3

設(shè)置對象中的某個屬性的值

_.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

對多個對象相同屬性的屬性值求和。

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}
}

生成一個隨機數(shù)，范圍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

判斷數(shù)據(jù)類型

_.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));

數(shù)據(jù)類型轉(zhuǎn)換

_.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"

重復(fù)多次某個元素

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

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