How to return string value?

I wrote this code

const link = "CKV0nSlxV8M"


const rendertest = async (link) => {
    const format = await ytdl(link, { quality: '22'})
    let test = JSON.stringify(format[0].url) 
        alert(test)  //string type
    return test
  
}

let finalValue = rendertest(link)
    
    
console.log(finalValue)

And I got this value from the test (string)

but exam value is not a String (Object)

I don't know which part I wrote wrong. I want the output of the same test and finalValue

When you define a function as async, behind the scenes it returns a promise. So, you have to wait for the promise to fulfill. Try this:

const link = "CKV0nSlxV8M"


const rendertest = async (link) => {
    const format = await ytdl(link, { quality: '22'});
    const test = JSON.stringify(format[0].url);

    return test
}

rendertest(link).then(finalValue => {
  console.log(finalValue)
}