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
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
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) // []
Delete
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
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
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”}
Read
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
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
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
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”
Util
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”]