JS数组精简的十三个技巧

1.删除数组的重复项

第一种方式
var fruits = ['banana', 'apple', 'orange', 'apple', 'orange', 'grape', 'watermelon']

var uniqueFruits = new Set(fruits)
console.log(uniqueFruits); // Set {'banana', 'apple', 'orange', 'grape', 'watermelon'}

var uniqueFruits = Array.from(new Set(fruits))
console.log(uniqueFruits); // [ 'banana', 'apple', 'orange', 'grape', 'watermelon' ]

第二种方式
var fruits = ['banana', 'apple', 'orange', 'apple', 'orange', 'grape', 'watermelon']

var uniqueFruits2 = [...new Set(fruits)]
console.log(uniqueFruits2); // [ 'banana', 'apple', 'orange', 'grape', 'watermelon' ]

2.替换数组中的特定值

var usernames = ['蜗牛0', '蜗牛1', '蜗牛2', '蜗牛3', '蜗牛4', '蜗牛5']
usernames.splice(0, 2, '蜗牛替换位置0', '蜗牛替换位置1')
console.log(usernames) // [ '蜗牛替换位置0', '蜗牛替换位置1', '蜗牛2', '蜗牛3', '蜗牛4', '蜗牛5' ]

3.Array.from 达到 .map 的效果

var friends = [
{ name: '小智', age: 22 },
{ name: '张三', age: 23 },
{ name: '李四', age: 24 },
{ name: '王二', age: 25 },
{ name: '麻子', age: 26 },
]
var friendsNames = Array.from(friends, ({ name }) => name)
console.log(friendsNames) // [ '小智', '张三', '李四', '王二', '麻子' ]

4.置空数组

var friends = [
{ name: '小智', age: 22 },
{ name: '张三', age: 23 },
{ name: '李四', age: 24 },
{ name: '王二', age: 25 },
{ name: '麻子', age: 26 },
]
friends.length = 0
console.log(friends) // []

5.将数组转换为对象

var usernames = ['蜗牛0', '蜗牛1', '蜗牛2', '蜗牛3']
var usernamesObj = { ...usernames }
console.log(usernamesObj) // { '0': '蜗牛0', '1': '蜗牛1', '2': '蜗牛2', '3': '蜗牛3' }

6.用数据填充数组

var array = new Array(10).fill('1')
console.log(array) // [ '1', '1', '1', '1', '1', '1', '1', '1', '1', '1' ]

7.数组合并

var fruits = ['apple', 'orange', 'banana']
var meat = ['beef', 'fish', 'poultry']
var vegetables = ['potato', 'tomato', 'cucumber']
var food = [...fruits, ...meat, ...vegetables]
console.log(food) // [ 'apple', 'orange', 'banana', 'beef', 'fish', 'poultry', 'potato', 'tomato', 'cucumber' ]

8.求两个数组的交集

var num0 = [0, 2, 4, 6, 8, 9]
var num1 = [0, 1, 3, 5, 8, 9]
var jiaoJi = [...new Set(num0)].filter(item => num1.includes(item))
console.log(jiaoJi) // [ 0, 8, 9 ]

9.从数组中删除虚值

var mixedArray = ['1', 0, false, null, '', NaN, 9, undefined, 'apple']
var trueArray = mixedArray.filter(Boolean)
console.log(trueArray) // [ '1', 9, 'apple' ]

10.从数组中获取随机值

var number = [0, 2, 4, 5, 7, 9, 22, 55]
var randomNumber = number[(Math.floor(Math.random() * (number.length)))]
console.log(randomNumber) // 9

11.反转数组

var number = [0, 2, 4, 5, 7, 9, 22, 55]
var numberReverse = number.reverse()
console.log(numberReverse) // [ 55, 22, 9, 7, 5, 4, 2, 0 ]

12.lastIndexOf() 方法

var number = [1, 5, 3, 8, 3, 9, 23, 65, 3, 99, 3, 4]
var lastNumber = number.lastIndexOf(3)
console.log(lastNumber) // 10

13.对数组中的所有值求和

var nums = [1, 5, 2, 6]
var sum = nums.reduce((x, y) => x + y)
console.log(sum) // 14