javascript常用的数组过滤和查找方法总结

const array = [
  {name: '11', age: 1},
  {name: '22', age: 2},
  {name: '33', age: 3}
];
const filterArray = array.filter(item => item.age > 2);
console.log(filterArray); // 输出新数组： [{name: '33', age: 3}]

let people = [

{ name: 'John', age: 25 },j

{ name: 'Jane', age: 18 },

{ name: 'Doe', age: 22 },

{ name: 'Jane', age: 20 }

];

let filteredPeople = people.filter(person =>

person.age > 20 && person.name.startsWith('J')

);

console.log(filteredPeople);

// 输出: [{ name: 'John', age: 25 }, { name: 'Jane', age: 20 }]

const array = ['11', '22', '33'];
const res = array.find(item=> item === '22');
console.log(res); // 输出 "22"


const array = [{name:'11'}, {name:'22'}, {name:'33'},{name:'22'}];
const res = array.find(item => item.name === '22');
console.log(res); // 输出 {name:'22'}

// 1.计算数组的和
const arr = [1, 2, 3, 4, 5];
const sum = arr.reduce((acc, curr) => acc + curr, 0); // 输出：15

// 2.统计每个元素出现的次数
const array = ['11', '22', '11', '22', '33'];
const fruitCount = array.reduce((acc, curr) => {
  acc[curr] = (acc[curr] || 0) + 1;
  return acc;
}, {}); 
// 输出：{ 11: 2, 22: 2, 33: 1 }


// 3.二维数组扁平一维数组
const arr2D = [[1, 2], [3, 4], [5, 6]];
const arrFlat = arr2D.reduce((acc, curr) => acc.concat(curr), []);
// 输出：[1, 2, 3, 4, 5, 6]

const names = ['11', '22', '33'];
const index = names.findIndex(name => name === '22');
console.log(index); // 输出 1

// 检查11是否为数组中的元素
const array = [11, 22, 33, 11];
const inc = array.includes(11);
console.log(inc)//true
 
//检查数组是否在第一个元素之外的其他位置包含22
const array = [11, 22, 33, 44, 55];
const inc = array.includes(22, 1);
console.log(inc) //true

// 匹配数组中33的索引
const array = [11, 22, 33, 44, 55];
const ind = array.indexOf(33);
console.log(ind)//2