怎么理解js方法

function greet(name) {
    console.log('Hello, ' + name);
}
greet('Alice'); // 输出: Hello, Alice

const greet = function(name) {
    console.log('Hello, ' + name);
};
greet('Bob'); // 输出: Hello, Bob

const greet = (name) => {
    console.log('Hello, ' + name);
};
greet('Charlie'); // 输出: Hello, Charlie

const person = {
    firstName: 'John',
    lastName: 'Doe',
    getFullName: function() {
        return this.firstName + ' ' + this.lastName;
    }
};
console.log(person.getFullName()); // 输出: John Doe

function asyncTask(value) {
    return new Promise((resolve, reject) => {
        setTimeout(() => resolve(value), 1000);
    });
}

asyncTask('result')
    .then(result => console.log(result))
    .catch(error => console.error(error));

async function runAsyncTask() {
    try {
        const result = await asyncTask('result');
        console.log(result);
    } catch (error) {
        console.error(error);
    }
}

runAsyncTask();