Javascript 迟延承诺

我有一个我似乎不知道如何解决的问题？编写一个函数，它接受一个值。此函数将返回一个承诺，该承诺将在2秒后解析。以下代码不应编辑，应使用promise对象

 function promised (val) {
     
    }
    
    // UNCOMMENT THESE TO TEST YOUR WORK!
     const createPromise = promised('wait for it...');
     createPromise.then((val) => console.log(val)); 
    // will log "wait for it..." to the console after 2 seconds

解释如下：

使用

setTimeout（）

，这是一种内置方法，可在指定的毫秒数后调用函数或计算表达式。

setTimeout（）

接受两个参数，第一个是回调函数，第二个是毫秒数。 1秒=1000ms，因此2秒=2000ms，依此类推

function promised (val) {
    // Create a new promise and resolve val after 2 seconds
    return new Promise(resolve => setTimeout(() => resolve(val), 2000)) //2000ms => 2 seconds
}



const createPromise = promised('wait for it...') // Pass in your message to promised function

createPromise
    .then(val => console.log(val))
    // Catch errors if any you don't need it here since we are always resolving the promise i just included it here so you know it's exist 
    .catch(err => console.log(err)) 

除非你百分之百确信承诺永远会解决问题，否则你应该始终使用.catch

例如：

function greeting(name) {

    return new Promise((resolve, reject) => setTimeout(() => {
        
        try {
            
            if (name.length <= 2) {
                throw new Error('Name must be more than two characters')
            }

        } catch (msg) {
            reject(msg)
        } 

        resolve(`Hello ${name}`)
        
        
    }, 2000))
}


greeting('ab')
    .then(res => console.log(res))
    .catch(err => console.log(err)) // Error: Name must be more than two characters

greeting('John')
    .then(res => console.log(res)) // Hello John
    .catch(err => console.log(err))

---

了解有关承诺的更多信息

问题在于，需要遵循这种特定的回答格式。请不要只发布代码作为回答，还要解释代码的作用以及如何解决问题。带有解释的答案通常更有帮助，质量更好，更容易吸引选票。更新了解释，练习是在不更改提供的框架格式的情况下使用promise对象。@YahyaElfaqir您当然可以借助此答案中提供的代码和规范问题来填写框架。@Markrottveel我认为代码已经足够清楚了，但我现在已经包含了解释

function greeting(name) {

    return new Promise((resolve, reject) => setTimeout(() => {
        
        try {
            
            if (name.length <= 2) {
                throw new Error('Name must be more than two characters')
            }

        } catch (msg) {
            reject(msg)
        } 

        resolve(`Hello ${name}`)
        
        
    }, 2000))
}


greeting('ab')
    .then(res => console.log(res))
    .catch(err => console.log(err)) // Error: Name must be more than two characters

greeting('John')
    .then(res => console.log(res)) // Hello John
    .catch(err => console.log(err))

const greetSomeone = async (name) => {

    try {

        // Note that you can't use await outside an async function
        const msg = await greeting(name) 
        console.log(msg)

    } catch (err) {
        console.log(err)
    }
}



greetSomeone('ac') // Error: Name must be more than two characters

greetSomeone('Michael') // Hello Michael