数组去重：

es5

[1,2,3,1,'a',1,'a'].filter(function(ele,index,array){    return index===array.indexOf(ele)})

es6

[...new Set([1,2,3,1,'a',1,'a'])]

数组摊平

const deepFlatten = arr => [].concat(...arr.map(v => Array.isArray(v) ? deepFlatten(v) : v));

求子集

//powerSet([1,2]) -> [[],[2],[1],[1,2]]function powerSet(arr = []) {                if (arr.length === 0) {                    return [[]];                } else {                    let head = arr.shift();                    let temp = powerSet(arr);                    return temp.concat(temp.map((e) => [head].concat(e)));                }            }