filter + indexOf

const arr = [1,2,2,4,null,null,'3','abc',3,5,4,1,2,2,4,null,null,'3','abc',3,5,4]

function handler(arr) {
    if(!Array.isArray(arr)){
        throw new Error('unique function params is not Array')
    }
}
function unique(arr) {
    handler(arr)
    return arr.filter((item,index)=>{
        return arr.indexOf(item) === index
    })
}

filter + hasOwnProperty

function unique(arr) {
    handler(arr)
    let obj = {}
    return arr.filter(item=>obj.hasOwnProperty(typeof item + item) ? false : (obj[typeof item + item] = true))
    
}

reduce + includes

function unique(arr) {
    handler(arr)
    arr.reduce((totalArr, currentItem)=>{
        return totalArr.includes(currentItem) ? totalArr : [...totalArr, currentItem]
    }, [])
}

Set + Array.form

function unique(arr) {
    handler(arr)
    let set = new Set(arr)
    return Array.form(set)
}

Set + 解构

function unique(arr) {
    handler(arr)
    let set = new Set(arr)
    return [...set]
}

Map

function unique(arr) {
    handler(arr)
    let map = new Map()
    let newArr = []
    for(let i = 0; i < arr.length; i++) {
        if(!map.has(arr[i])) {
            map.set(arr[i], true)
            newArr.push(arr[i])
        }
    }
    
    return newArr
}