How do you make javascript code execute *in order*

Question

Okay, so I appreciate that Javascript is not C# or PHP, but I keep coming back to an issue in Javascript - not with JS itself but my use of it.

I have a function:

Answer 1

One of the best solutions for handling all async requests is the 'Promise'.
The Promise object represents the eventual completion (or failure) of an asynchronous operation.

Example:

let myFirstPromise = new Promise((resolve, reject) => {
  // We call resolve(...) when what we were doing asynchronously was successful, and reject(...) when it failed.
  // In this example, we use setTimeout(...) to simulate async code. 
  // In reality, you will probably be using something like XHR or an HTML5 API.
  setTimeout(function(){
    resolve("Success!"); // Yay! Everything went well!
  }, 250);
});  

myFirstPromise.then((successMessage) => {
  // successMessage is whatever we passed in the resolve(...) function above.
  // It doesn't have to be a string, but if it is only a succeed message, it probably will be.
  console.log("Yay! " + successMessage);
});

Promise

If you have 3 async functions and expect to run in order, do as follows:

let FirstPromise = new Promise((resolve, reject) => {
    FirstPromise.resolve("First!");
});
let SecondPromise = new Promise((resolve, reject) => {

});
let ThirdPromise = new Promise((resolve, reject) => {

});
FirstPromise.then((successMessage) => {
  jQuery.ajax({
    type: "type",
    url: "url",
    success: function(response){
        console.log("First! ");
        SecondPromise.resolve("Second!");
    },
    error: function() {
        //handle your error
    }  
  });           
});
SecondPromise.then((successMessage) => {
  jQuery.ajax({
    type: "type",
    url: "url",
    success: function(response){
        console.log("Second! ");
        ThirdPromise.resolve("Third!");
    },
    error: function() {
       //handle your error
    }  
  });    
});
ThirdPromise.then((successMessage) => {
  jQuery.ajax({
    type: "type",
    url: "url",
    success: function(response){
        console.log("Third! ");
    },
    error: function() {
        //handle your error
    }  
  });  
});

With this approach, you can handle all async operation as you wish.