数组去重、扁平.js

/**
 * 数组去重
 */

const unique = array => [...new Set(array)];

const unique = array => Array.from(new Set(array));

const unique = array => {
  return array.filter((value, key) => array.indexOf(value) === key);
};

const unique = array => {
  var container = {};
  return array.filter((item, index) =>
    container.hasOwnProperty(item) ? false : (container[item] = true)
  );
};

/**
 * 数组扁平处理
 */

// 基本实现
const flat = array => {
  let result = [];
  for (let i = 0, len = array.length; i < len; i++) {
    if (Array.isArray(array[i])) {
      result = result.concat(flat(array[i]));
    } else {
      result.push(array[i]);
    }
  }
  return result;
};

// reduce 实现
const flat = array =>
  array.reduce(
    (target, current) =>
      Array.isArray(current)
        ? target.concat(flat(current))
        : target.concat(current),
    []
  );

// 指定深度
const flattenByDeep = (array, deep = Infinity) =>
  array.reduce(
    (target, current) =>
      Array.isArray(current) && deep > 1
        ? target.concat(flattenByDeep(current, deep - 1))
        : target.concat(current),
    []
  );