数组去重

tip

考察JS的基础功底

ES6 Set

const uniqueArr = [...new Set(arr)];
const uniqueArr = Array.from(new Set(arr));

reduce

function unique(arr){
    // 先排序，如果重复，则上一个下标的内容一样
    return arr.sort().reduce((acc, current) => {
        if(acc.length == 0 || acc[acc.length - 1] !== current){
            acc.push(current);
        }
        return acc;
    }, [])
}

filter

function unique(arr){
    return arr.filter((element, index, array) => {
        return array.indexOf(element) == index;
    })
}