js评价代码

console.log(undeclaredVar); // ReferenceError: undeclaredVar is not defined

let declaredVar = 'Hello World';
console.log(declaredVar);

function test() {
    var x = 10;
}
console.log(x); // ReferenceError: x is not defined

function test() {
    let x = 10;
}
// console.log(x); // 这里会报错，x在函数外部不可访问

function asyncTask(callback) {
    setTimeout(() => callback('done'), 1000);
}

asyncTask(result => {
    console.log(result);
    asyncTask(result2 => {
        console.log(result2);
    });
});

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

async function runTasks() {
    const result1 = await asyncTask();
    console.log(result1);
    const result2 = await asyncTask();
    console.log(result2);
}

runTasks();

function setupEventListener() {
    const button = document.getElementById('myButton');
    button.addEventListener('click', handleClick);

    // 清理事件监听
    button.removeEventListener('click', handleClick);
}