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。
Array
Create
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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]
Read
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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]
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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) // []
Delete
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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]
Format
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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]
Object
Create
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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}
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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"}
Read
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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
Update
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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} }
Number
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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
Data Type
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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
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_.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"
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Util
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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"]
