A promise chain with setTimeout in javascript.

1-promise.js

// Demo http://jsbin.com/qevetiqavu/edit?js,output
var one = function(i) {
  return new Promise((resolve, reject) => {
    setTimeout(() => {
      console.log(`setTimeout ${i}`);
      
      if (i < 0) {
        reject(i);
      }
      else if (i >= 5) {
        resolve(i);
      }
      else {
        return one(i + 1)
          .then(i => { resolve(i); })
          .catch(err => { reject(err); });
      }
    }, 1000);
  });
}

var two = function(i) {
  return one(i)
    .then(i => {
      return i * 2;
    })
    .catch(err => { throw err; });
}

two(1)
  .then(i => console.log(`Done ${i}`))
  .catch(err => console.log(`Error: ${err}`));

2-promise.js

// A slight variation of the first example, where we pass in a value.
// Demo http://jsbin.com/yegovopuya/1/edit?js,output
var one = function(i, original) {
  original = original || i;
  
  return new Promise((resolve, reject) => {
    setTimeout(() => {
      console.log(`setTimeout ${i}`);
      
      if (i < 0) {
        reject(i);
      }
      else if (i >= original + 4) {
        resolve(i);
      }
      else {
        return one(i + 1, original)
          .then(i => { resolve(i); })
          .catch(err => { reject(err); });
      }
    }, 1000);
  });
}

var two = function(i) {
  i = 100 + i;
  
  return one(i)
    .then(i => {
      return i * 2;
    })
    .catch(err => { throw err; });
}

two(1)
  .then(i => console.log(`Done ${i}`))
  .catch(err => console.log(`Error: ${err}`));