const arr = [1, 5, '5', 'a','c','a' true, true, false, false, 'true', 'a', {}, {}];

思路：

1. 使用set,然后转数组
2. 循环，通过数组类似包含的方法判断
3. 通过Map, 空间换时间

1. Array.from & Set

The Array.from() static method creates a new, shallow-copied Array instance from an array-like or iterable object

Array.from(new Set(arr))

2.indexof,includes,filter

const unique = arr => {
    const res = [];
    for (let i = 0,len = arr.length; i < len; i++) {
      if (res.indexOf(arr[i]) === -1) {
        res.push(arr[i]);
      }
    }
    return res;
}

3. map

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