lodash与30-seconds-code中的数组对象

1. maxBy: 数组对象中返回指定属性中最大的值

lodash

var objects = [{ 'n': 1 }, { 'n': 2 }];

_.maxBy(objects, function(o) { return o.n; });
// => { 'n': 2 }

// The `_.property` iteratee shorthand.
_.maxBy(objects, 'n');
// => { 'n': 2 }

ES6

const maxBy = (arr, fn) => Math.max(...arr.map(typeof fn === 'function' ? fn : val => val[fn]));

maxBy([{ n: 4 }, { n: 2 }, { n: 8 }, { n: 6 }], o => o.n); // 8
maxBy([{ n: 4 }, { n: 2 }, { n: 8 }, { n: 6 }], 'n'); // 8

2.differenceBy: 找不同

lodash

_.differenceBy([3.1, 2.2, 1.3], [4.4, 2.5], Math.floor);
// => [3.1, 1.3]
 
// The `_.property` iteratee shorthand.
_.differenceBy([{ 'x': 2 }, { 'x': 1 }], [{ 'x': 1 }], 'x');
// => [{ 'x': 2 }]

ES6

const differenceBy = (a, b, fn) => {
  const s = new Set(b.map(v => fn(v)));
  return a.filter(x => !s.has(fn(x)));
};
differenceBy([2.1, 1.2], [2.3, 3.4], Math.floor); // [1.2]
differenceBy([{ x: 2 }, { x: 1 }], [{ x: 1 }], v => v.x); // [ { x: 2 } ]

3.differenceWith: 排除一个指定的数组对象

lodash

var objects = [{ 'x': 1, 'y': 2 }, { 'x': 2, 'y': 1 }];
 
_.differenceWith(objects, [{ 'x': 1, 'y': 2 }], _.isEqual);
// => [{ 'x': 2, 'y': 1 }]

ES6

const differenceWith = (arr, val, comp) => arr.filter(a => val.findIndex(b => comp(a, b)) === -1);
differenceWith([1, 1.2, 1.5, 3, 0], [1.9, 3, 0], (a, b) => Math.round(a) === Math.round(b)); // [1, 1.2]

4.intersectionBy： 返回一个包含所有传入数组交集元素的新数组。

lodash

_.intersectionBy([2.1, 1.2], [4.3, 2.4], Math.floor);
// => [2.1]
 
// The `_.property` iteratee shorthand.
_.intersectionBy([{ 'x': 1 }], [{ 'x': 2 }, { 'x': 1 }], 'x');
// => [{ 'x': 1 }]

ES6

const intersectionBy = (a, b, fn) => {
  const s = new Set(b.map(x => fn(x)));
  return a.filter(x => s.has(fn(x)));
};
intersectionBy([2.1, 1.2], [2.3, 3.4], Math.floor); // [2.1]

5.intersectionWith: 返回一个包含所有传入数组交集元素的新数组。

lodash

var objects = [{ 'x': 1, 'y': 2 }, { 'x': 2, 'y': 1 }];
var others = [{ 'x': 1, 'y': 1 }, { 'x': 1, 'y': 2 }];
 
_.intersectionWith(objects, others, _.isEqual);
// => [{ 'x': 1, 'y': 2 }]

ES6

const intersectionWith = (a, b, comp) => a.filter(x => b.findIndex(y => comp(x, y)) !== -1);
intersectionWith([1, 1.2, 1.5, 3, 0], [1.9, 3, 0, 3.9], (a, b) => Math.round(a) === Math.round(b)); // [1.5, 3, 0]

6.pullAllBy 移除指定数组对象

lodash

var array = [{ 'x': 1 }, { 'x': 2 }, { 'x': 3 }, { 'x': 1 }];
 
_.pullAllBy(array, [{ 'x': 1 }, { 'x': 3 }], 'x');
console.log(array);
// => [{ 'x': 2 }]

ES6

const pullBy = (arr, ...args) => {
  const length = args.length;
  let fn = length > 1 ? args[length - 1] : undefined;
  fn = typeof fn == 'function' ? (args.pop(), fn) : undefined;
  let argState = (Array.isArray(args[0]) ? args[0] : args).map(val => fn(val));
  let pulled = arr.filter((v, i) => !argState.includes(fn(v)));
  arr.length = 0;
  pulled.forEach(v => arr.push(v));
};
var myArray = [{ x: 1 }, { x: 2 }, { x: 3 }, { x: 1 }];
pullBy(myArray, [{ x: 1 }, { x: 3 }], o => o.x); // myArray = [{ x: 2 }]

7.pullAllWith

lodash

var array = [{ 'x': 1, 'y': 2 }, { 'x': 3, 'y': 4 }, { 'x': 5, 'y': 6 }];
 
_.pullAllWith(array, [{ 'x': 3, 'y': 4 }], _.isEqual);
console.log(array);
// => [{ 'x': 1, 'y': 2 }, { 'x': 5, 'y': 6 }]

ES6
暂无

8.unionBy: 返回一个新的联合数组

lodash

_.unionBy([2.1], [1.2, 2.3], Math.floor);
// => [2.1, 1.2]
 
// The `_.property` iteratee shorthand.
_.unionBy([{ 'x': 1 }], [{ 'x': 2 }, { 'x': 1 }], 'x');
// => [{ 'x': 1 }, { 'x': 2 }]

ES6

const unionBy = (a, b, fn) => {
  const s = new Set(a.map(v => fn(v)));
  return Array.from(new Set([...a, ...b.filter(x => !s.has(fn(x)))]));
};
unionBy([2.1], [1.2, 2.3], Math.floor); // [2.1, 1.2]

9.unionWith： 返回一个新的联合数组

lodash

var objects = [{ 'x': 1, 'y': 2 }, { 'x': 2, 'y': 1 }];
var others = [{ 'x': 1, 'y': 1 }, { 'x': 1, 'y': 2 }];
 
_.unionWith(objects, others, _.isEqual);
// => [{ 'x': 1, 'y': 2 }, { 'x': 2, 'y': 1 }, { 'x': 1, 'y': 1 }]

ES6

const unionWith = (a, b, comp) => Array.from(new Set([...a, ...b.filter(x => a.findIndex(y => comp(x, y)) === -1)]));
unionWith([1, 1.2, 1.5, 3, 0], [1.9, 3, 0, 3.9], (a, b) => Math.round(a) === Math.round(b)); // [1, 1.2, 1.5, 3, 0, 3.9]

10.uniqBy: 返回新的去重后的数组。

lodash

_.uniqBy([2.1, 1.2, 2.3], Math.floor);
// => [2.1, 1.2]
 
// The `_.property` iteratee shorthand.
_.uniqBy([{ 'x': 1 }, { 'x': 2 }, { 'x': 1 }], 'x');
// => [{ 'x': 1 }, { 'x': 2 }]

ES6
暂无

11.uniqWith:返回新的去重后的数组。

lodash

var objects = [{ 'x': 1, 'y': 2 }, { 'x': 2, 'y': 1 }, { 'x': 1, 'y': 2 }];
 
_.uniqWith(objects, _.isEqual);
// => [{ 'x': 1, 'y': 2 }, { 'x': 2, 'y': 1 }

ES6
暂无

12.xorBy: 返回过滤值后的新数组

lodash

_.xorBy([2.1, 1.2], [2.3, 3.4], Math.floor);
// => [1.2, 3.4]
 
// The `_.property` iteratee shorthand.
_.xorBy([{ 'x': 1 }], [{ 'x': 2 }, { 'x': 1 }], 'x');
// => [{ 'x': 2 }]

ES6
暂无

13.xorWith：返回过滤值后的新数组。

lodash

var objects = [{ 'x': 1, 'y': 2 }, { 'x': 2, 'y': 1 }];
var others = [{ 'x': 1, 'y': 1 }, { 'x': 1, 'y': 2 }];
 
_.xorWith(objects, others, _.isEqual);
// => [{ 'x': 2, 'y': 1 }, { 'x': 1, 'y': 1 }]

ES6
暂无

14.castArray：返回转换后的数组

lodash

_.castArray(1);
// => [1]
 
_.castArray({ 'a': 1 });
// => [{ 'a': 1 }]
 
_.castArray('abc');
// => ['abc']
 
_.castArray(null);
// => [null]
 
_.castArray(undefined);
// => [undefined]
 
_.castArray();
// => []
 
var array = [1, 2, 3];
console.log(_.castArray(array) === array);
// => true

ES6

const castArray = val => (Array.isArray(val) ? val : [val]);
castArray('foo'); // ['foo']
castArray([1]); // [1]

15.filter:返回新的函数

lodash

var objects = [
  { 'a': 2, 'b': 1 },
  { 'a': 1, 'b': 2 }
];
 
_.filter(objects, _.conforms({ 'b': function(n) { return n > 1; } }));
// => [{ 'a': 1, 'b': 2 }]

ES6
暂无

16._.times: 返回新的常量函数。

lodash

var objects = _.times(2, _.constant({ 'a': 1 }));
 
console.log(objects);
// => [{ 'a': 1 }, { 'a': 1 }]
 
console.log(objects[0] === objects[1]);
// => true

ES6

const times = (n, fn, context = undefined) => {
  let i = 0;
  while (fn.call(context, i) !== false && ++i < n) {}
};
var output = '';
times(5, i => (output += i));
console.log(output); // 01234

17.filter: 返回回调函数 callback。

lodash

var users = [
  { 'user': 'barney', 'age': 36, 'active': true },
  { 'user': 'fred',   'age': 40, 'active': false }
];
 
// The `_.matches` iteratee shorthand.
_.filter(users, _.iteratee({ 'user': 'barney', 'active': true }));
// => [{ 'user': 'barney', 'age': 36, 'active': true }]
 
// The `_.matchesProperty` iteratee shorthand.
_.filter(users, _.iteratee(['user', 'fred']));
// => [{ 'user': 'fred', 'age': 40 }]
 
// The `_.property` iteratee shorthand.
_.map(users, _.iteratee('user'));
// => ['barney', 'fred']
 
// Create custom iteratee shorthands.
_.iteratee = _.wrap(_.iteratee, function(iteratee, func) {
  return !_.isRegExp(func) ? iteratee(func) : function(string) {
    return func.test(string);
  };
});
 
_.filter(['abc', 'def'], /ef/);
// => ['def']

ES6
暂无

18.filter：返回回调函数 callback。

lodash

var users = [
  { 'user': 'barney', 'age': 36, 'active': true },
  { 'user': 'fred',   'age': 40, 'active': false }
];
 
// The `_.matches` iteratee shorthand.
_.filter(users, _.iteratee({ 'user': 'barney', 'active': true }));
// => [{ 'user': 'barney', 'age': 36, 'active': true }]
 
// The `_.matchesProperty` iteratee shorthand.
_.filter(users, _.iteratee(['user', 'fred']));
// => [{ 'user': 'fred', 'age': 40 }]
 
// The `_.property` iteratee shorthand.
_.map(users, _.iteratee('user'));
// => ['barney', 'fred']
 
// Create custom iteratee shorthands.
_.iteratee = _.wrap(_.iteratee, function(iteratee, func) {
  return !_.isRegExp(func) ? iteratee(func) : function(string) {
    return func.test(string);
  };
});
 
_.filter(['abc', 'def'], /ef/);
// => ['def']

ES6
暂无

19.filter:返回新的函数。

lodash

var objects = [
  { 'a': 1, 'b': 2, 'c': 3 },
  { 'a': 4, 'b': 5, 'c': 6 }
];
 
_.filter(objects, _.matches({ 'a': 4, 'c': 6 }));
// => [{ 'a': 4, 'b': 5, 'c': 6 }]

20.merge:合并对象

lodash

var object = {
  'a': [{ 'b': 2 }, { 'd': 4 }]
};
 
var other = {
  'a': [{ 'c': 3 }, { 'e': 5 }]
};
 
_.merge(object, other);
// => { 'a': [{ 'b': 2, 'c': 3 }, { 'd': 4, 'e': 5 }] }

ES6

const merge = (...objs) =>
  [...objs].reduce(
    (acc, obj) =>
      Object.keys(obj).reduce((a, k) => {
        acc[k] = acc.hasOwnProperty(k) ? [].concat(acc[k]).concat(obj[k]) : obj[k];
        return acc;
      }, {}),
    {}
  );
const object = {
  a: [{ x: 2 }, { y: 4 }],
  b: 1
};
const other = {
  a: { z: 3 },
  b: [2, 3],
  c: 'foo'
};
merge(object, other); // { a: [ { x: 2 }, { y: 4 }, { z: 3 } ], b: [ 1, 2, 3 ], c: 'foo' }

21.minBy:数组对象中返回最小的值。

lodash

var objects = [{ 'n': 1 }, { 'n': 2 }];
 
_.minBy(objects, function(o) { return o.n; });
// => { 'n': 1 }
 
// The `_.property` iteratee shorthand.
_.minBy(objects, 'n');
// => { 'n': 1 }

ES6

const minBy = (arr, fn) => Math.min(...arr.map(typeof fn === 'function' ? fn : val => val[fn]));
minBy([{ n: 4 }, { n: 2 }, { n: 8 }, { n: 6 }], o => o.n); // 2
minBy([{ n: 4 }, { n: 2 }, { n: 8 }, { n: 6 }], 'n'); // 2

22. sumBy:数组对象中返回总和

lodash

var objects = [{ 'n': 4 }, { 'n': 2 }, { 'n': 8 }, { 'n': 6 }];
 
_.sumBy(objects, function(o) { return o.n; });
// => 20
 
// The `_.property` iteratee shorthand.
_.sumBy(objects, 'n');
// => 20

ES6

const sumBy = (arr, fn) => arr.map(typeof fn === 'function' ? fn : val => val[fn]).reduce((acc, val) => acc + val, 0);
sumBy([{ n: 4 }, { n: 2 }, { n: 8 }, { n: 6 }], o => o.n); // 20
sumBy([{ n: 4 }, { n: 2 }, { n: 8 }, { n: 6 }], 'n'); // 20