数组处理（es6）

let a = [1,2,1,4,6,5,5,'pen','apple']
let b = [2,3,4]

// 去重
let unique = [...new Set(a)]
console.log(unique)// [ 1, 2, 4, 6, 5, 'pen', 'apple' ]

// 并集
let union = [...a,...b]
console.log(union)

// 交集
let intersection = a.filter(item => b.includes(item))
console.log(intersection)//[ 2, 4 ]

//差集
let diff = a.filter(item => !b.includes(item))
console.log(diff)//[ 1, 1, 6, 5, 5, 'pen', 'apple' ]

//升序排序
let ascending = a.sort((a,b)=>{return a-b})
console.log(ascending)//[ 1, 1, 2, 4, 5, 5, 6, 'pen', 'apple' ]

// 降序排序
let dec = a.sort((a,b)=>{return b-a})
console.log(dec)//[ 6, 5, 5, 4, 2, 1, 1, 'pen', 'apple' ]

//字母排序
let lettersort = a.sort()
console.log(lettersort)//[ 1, 1, 2, 4, 5, 5, 6, 'apple', 'pen' ]

// 去掉无内容的元素
soure = [1,undefined,null,'',2,[],0]
soure = soure.filter((item) => !!item);
console.log('soure',soure)//soure [ 1, 2, [] ]