100.30 seconds of es6 之数组篇(3)

[neptoo]

30 seconds of es6 之数组篇

9.countOccurrences 检测出现的次数

const countOccurrences = (arr, val) => arr.reduce((a, v) => (v === val ? a + 1 : a), 0);
countOccurrences([1, 1, 2, 1, 2, 3], 1); // 3

10.deepFlatten 扁平化数组

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

deepFlatten([1,[2,[3],4]]);  //[1,2,3,4]

11.difference 找差异数

const difference = (a, b) => {
  const s = new Set(b);
  return a.filter(x => !s.has(x));
};

difference([1,2,3,4],[3,4,5,6]);  // [1,2] 返回前一个数组中与第二个数组不同的

12.dropWhile 去除不符合条件的值

const dropWhile = (arr, func) => {
  while (arr.length > 0 && !func(arr[0])) arr = arr.slice(1);
  return arr;
}

dropWhile([1, 2, 3, 4], n => n >= 3); // [3,4]

查看原文

JavaScript 工具函数大全（新）

30-seconds-of-code