数组处理 reduce() 数组的归并方法

1. 获取数组的最小元素

const getSmallest = (arr) =>
  arr.reduce((smallest, num) => Math.min(smallest, num));
const arr = [13, 7, 11, 3, 9, 15, 17];
console.log(getSmallest(arr)); // 3

2. 获取数组的最大元素

const getLargest = (arr) =>
  arr.reduce((largest, num) => Math.max(largest, num));
const arr = [13, 7, 11, 3, 9, 15, 17];
console.log(getLargest(arr)); // 17

3. 获取数组的平均值  reduce() 是数组的归并方法

const getAverage = (arr) => arr.reduce((sum, num) => sum + num, 0) / arr.length;
const arr = [5, 13, 9, 11, 10, 15, 7];
const average = getAverage(arr);
console.log(average); // 10

4. 从数组中删除重复项

const removeDuplicates = (arr) => [...new Set(arr)];
const arr = [1, 2, 3, 4, 5, 3, 1, 2, 5];
const distinct = removeDuplicates(arr);
console.log(distinct); // [1, 2, 3, 4, 5]

 

5. 打乱数组

const shuffleArray = (arr) => arr.sort(() => Math.random() - 0.5);
const arr = [1, 2, 3, 4, 5];
// [ 5, 2, 4, 1, 3 ] (varies)
console.log(shuffleArray(arr));

6. 按对象属性对数组进行分组

const groupBy = (arr, groupFn) =>
  arr.reduce(
    (grouped, obj) => ({
      ...grouped,
      [groupFn(obj)]: [...(grouped[groupFn(obj)] || []), obj],
    }),
    {}
  );
const people = [
  { name: 'Matt' },
  { name: 'Sam' },
  { name: 'John' },
  { name: 'Mac' },
];
const groupedByNameLength = groupBy(people, (person) => person.name.length);
/**
{
  '3': [ { name: 'Sam' }, { name: 'Mac' } ],
  '4': [ { name: 'Matt' }, { name: 'John' } ]
}
 */
console.log(groupedByNameLength);

7. 反转字符串

const reverseString = (str) => str.split('').reverse().join('');
const reverse = reverseString('javascript');
console.log(reverse); // tpircsavaj

8. 将蛇形字符串转换为驼峰大小写

const snakeToCamelCase = (s) =>
  s.toLowerCase().replace(/(_\w)/g, (w) => w.toUpperCase().substr(1));
const str1 = 'learn_javascript';
const str2 = 'coding_beauty';
console.log(snakeToCamelCase(str1)); // learnJavaScript
console.log(snakeToCamelCase(str2)); // codingBeauty