const distinct = arr => arr.sort().reduce( (init, current) => {
    
    if (init.length === 0 || init[init.length - 1] !== current) {
        init.push( current );
    }
    return init;
}, []);

let arr = [1,2,1,2,3,5,4,5,3,4,4,4,4];
console.log(distinct(arr)); // 输出[1, 2, 3, 4, 5]

const distinct = arr => arr.filter( (element, index, self) => {
    return self.indexOf( element ) === index;
});

let arr = [1,2,1,2,3,5,4,5,3,4,4,4,4];
console.log(distinct(arr)); // 输出[1, 2, 3, 4, 5]

const distinct = arr => arr.filter( (element, index, self) => {
    return self.indexOf( element ) !== index;
});

let arr = ['🐑', 1, 2, '🐑', '🐑', 3, '🐑', '🐑', 3]
console.log(distinct(arr)); // 输出["🐑", "🐑", "🐑", "🐑", 3]

function arrayUniqueObject(arr,name){
    var hash = {};
        return arr.reduce(function (item, next) {
            hash[next[name]] ? '' : hash[next[name]] = true && item.push(next);
            return item;
    }, []);
}

let arr = [
    {id:1,name:'小明'},
    {id:1,name:'小红'},
    {id:2,name:'小智'}
]

console.log(arrayUniqueObject(arr,'id')) // 输出[{id:1,name:'小明'},{id:2,name:'小智'}]

const flattenDeep = arr => Array.isArray(arr)
  ? arr.reduce( (a, b) => [...a, ...flattenDeep(b)] , [])
  : [arr]

console.log(flattenDeep([1, [[2], [3, [4]], 5]])) // 输出[1, 2, 3, 4, 5]

console.log([1, [[2], [3, [4]], 5]].flat(3)) // 输出[1, 2, 3, 4, 5]