[chncdcksn]

.then() does create a new promise. Return Promise.reject() in the fulfillment function to reject the new promise.

  somethingThatReturnsPromiseWithoutError()
    .then((res) => {
      return Promise.reject("some error");
    })
    .catch((err) => {
      console.log(err); // => some error
    });

Promise.resolve() and Promise.reject() return a promise resolved or rejected to the value passed in the first argument. Returning a promise in the fulfillment function passed to .then() chains the promises together.

  somethingThatReturnsPromise()
    .then((foo) => {
      return foo.bar;
      // Or if you like it more verbose
      return Promise.resolve(foo.bar);
      // Or pass bar to a function modifying bar that returns a promise
      return modifyBarReturnPromise(foo.bar);
    })
    .then((newBar) => {
      console.log(newBar);
    });

In your case, if you need step1Val in next promise chain, I personally do this, however people more familiar with promises may know of a better way to do it (maybe with something like Promise.all() or Promise.props() in the BlueBird library).

  somethingThatReturnsPromise()
    .then((first) => {
       doSomethingWithFirstAndReturnPromise(first)
         .then((second) => {
           console.log(first + second);
         });
    });

[mikekchar]

It took me a while to understand this correct response because I couldn't understand the documentation for promises. For the benefit of any other person who was likewise confused...

then() returns a new promise resolved to the return value of the function. However, if that value is itself a promise, then it follows the promise chain and passes the eventual state to the next then()/catch() call.