JSFiddle - React, Tailwind, and code Playground

JavaScript

const getNumbers  = () => {
  return new Promise(function(resolve, reject) {

    console.log("In function getNumbers");
    var data = [1,2,3,4,5,6,7,8,9];
    resolve(data);
  });
};

const delay = (number, t) => {
	return new Promise((resolve) => {
      setTimeout(() => { 
        //make a http request
        resolve(
          getHtml("https://jsonplaceholder.typicode.com/posts/"+number)
          .then(function(post) {
            console.log('title', post.title)
            return post.title;
          })
        )
      }, t)
  	})
    
}
          
const getHtml = (webUrl) => {
    return fetch(webUrl)
        .then(function(res) {
            return res.json();
        });
}

getNumbers()
    .then(numbersArray => {
        //Supposed to return array of posts title
        return Promise.all(numbersArray.map((number, i) => {
          console.log("Reading number" + number);
          return delay(number, 10000*(i+1));//make a request each ten seconds
        }))
        .then(postTitlesArray => {
          //Shows array of undefined
            console.log(postTitlesArray)
    		});
    })