Js中的Object.entries()基本知识详细分析(附Demo)

const obj = { a: 1, b: 2, c: 3 };
const entries = Object.entries(obj);
console.log(entries);
// 输出: [['a', 1], ['b', 2], ['c', 3]]

const emptyObj = {};
const entries = Object.entries(emptyObj);
console.log(entries);
// 输出: []

const obj = { a: 1, b: 2, c: 3 };

console.log(Object.keys(obj));
// 输出: ['a', 'b', 'c']

console.log(Object.values(obj));
// 输出: [1, 2, 3]

console.log(Object.entries(obj));
// 输出: [['a', 1], ['b', 2], ['c', 3]]

try {
    console.log(Object.entries(null));
} catch (e) {
    console.error(e);
    // 输出: TypeError: Cannot convert undefined or null to object
}

const obj = { x: 10, y: 20, z: 30 };

for (const [key, value] of Object.entries(obj)) {
    console.log(`${key}: ${value}`);
}
// 输出:
// x: 10
// y: 20
// z: 30

const obj = { a: 1, b: 2, c: 3, d: 4 };

const filteredEntries = Object.entries(obj).filter(([key, value]) => value > 2);
console.log(filteredEntries);
// 输出: [['c', 3], ['d', 4]]

const obj = { name: 'Alice', age: 25 };

const transformedEntries = Object.entries(obj).map(([key, value]) => {
    return [key, typeof value === 'string' ? value.toUpperCase() : value];
});

const newObj = Object.fromEntries(transformedEntries);
console.log(newObj);
// 输出: { name: 'ALICE', age: 25 }

const nestedObj = {
    user: {
        name: 'Bob',
        age: 30
    },
    location: {
        city: 'New York',
        country: 'USA'
    }
};

const nestedEntries = Object.entries(nestedObj).flatMap(([key, value]) =>
    Object.entries(value).map(([subKey, subValue]) => [`${key}.${subKey}`, subValue])
);

console.log(nestedEntries);
// 输出: [['user.name', 'Bob'], ['user.age', 30], ['location.city', 'New York'], ['location.country', 'USA']]

const entries = [['a', 1], ['b', 2], ['c', 3]];

const obj = Object.fromEntries(entries);
console.log(obj);
// 输出: { a: 1, b: 2, c: 3 }

const obj = { apple: 10, banana: 20, cherry: 30 };

const total = Object.entries(obj).reduce((sum, [key, value]) => sum + value, 0);
console.log(total);
// 输出: 60

const params = { name: 'Alice', age: 25, city: 'Wonderland' };

const queryString = Object.entries(params)
    .map(([key, value]) => `${encodeURIComponent(key)}=${encodeURIComponent(value)}`)
    .join('&');

console.log(queryString);
// 输出: 'name=Alice&age=25&city=Wonderland'

const person = {
            name: '王二',
            age: 18,
            sex: '男',
            say() {
                console.log('说话');
            }
        }
 
        const obj1 = Object.entries(person)//返回对象的键值对数组
        const obj2 = Object.fromEntries(obj1);//通过上述的键值对数组，返回对应的对象
        console.log(obj1);
        console.log(obj2);