有哪些方法实现数组去重
1 let a = [1,1,1,3,5,6]
const b = Array.from(new Set(a))
2 const list = []
const arr = new Map()
const c = a.forEach((item) => {
if(!arr.has(item)){
arr.set(item,true)
list.push(item)
}
})

3
const list1 = []
a.forEach((item) => {
if(list1.indexOf(item) === -1) {
list1.push(item)
}
})