create a fake promise code example

Example 1: return new Promise(res => {

// the execution: catch -> then
new Promise((resolve, reject) => {

  throw new Error("Whoops!");

}).catch(function(error) {

  alert("The error is handled, continue normally");

}).then(() => alert("Next successful handler runs"));

Example 2: resolve vs return promise js

In simple terms, inside a then handler function:

A) When x is a value (number, string, etc):
	- return x is equivalent to return Promise.resolve(x)
	- throw x is equivalent to return Promise.reject(x)

B) When x is a Promise that is already settled (not 
pending anymore):
	- return x is equivalent to return Promise.resolve(x), 
      if the Promise was already resolved.
	- return x is equivalent to return Promise.reject(x), 
      if the Promise was already rejected.
      
C) When x is a Promise that is pending:
	- return x will return a pending Promise, and it will 
    be evaluated on the subsequent then.
Read more on this topic on the Promise.prototype.then() docs.