SOURCE

console.log('start here')

const foo = () => (new Promise((resolve, reject) => {
    console.log('first promise constructor')
    let promise1 = new Promise((resolve, reject) => {
        console.log('second promise constructor')
        setTimeout(()=>{
            console.log('setTimeout here')
        resolve('promise2')
        },0)
        resolve('promise1')
    })
    resolve('promise0')
    promise1.then(arg => {
        console.log(arg)
    })
}))

foo().then(arg => {
    console.log(arg)
})

console.log('end here')