1. Set 结构
[...new Set(arr)]
2. reduce
arr.reduce((pre, item, index) => {
if(!pre.includes(item)) {
pre.push(item)
}
return pre
}, [])
3. filter
let arr = [1, 1, 2, 3, 4, 5, 4]
let newArr = arr.filter((item, index) => {
return index === arr[item]
})
4. forEach 新创建一个数组
let arr = [1, 1, 2, 3, 4, 5, 4]
let newArr = []
arr.filter((item, index) => {
if(!newArr.includes(item)) {
newArr.push(item)
}
})