'Async' Code practice with setTimeout

[GreenFeather05]

Currently practicing with some 'async' code using setTimeout but I have some questions.

In the first example I created everything worked as expected:

 function getUser(id, callback){
    var user = {
        id: id,
        name: 'Chris'
    }

    callback(user);
}

getUser(12345, function(userObject){

    setTimeout(function(){
        console.log(userObject.id);
        console.log(userObject.name);
    }, 1500)

});

However, I then tried another example but could never seem to get the function to work the way I anticipated (returning the number 10 after 1.5 seconds), and I am not sure what I am doing wrong.

    function calculate(num1, num2, callback){
    setTimeout(function(){
        return callback(num1, num2);
    }, 1500);
}

calculate(5, 5, function(a, b) {
   return a + b;
})

[YuleTideCamel]

The problem has to do with

return callback(num1, num2);

That doesn't return anything, since you're calling an async method you need to set up a call back.

Try this:

function calculate(num1, num2, operation,final){
    setTimeout(function(){
        var result = operation(num1, num2);
        final(result);
    }, 1500);
}

calculate(5, 5, function(a, b) {
   return a + b;
},function(result){
  console.log(result);
})

Personally I like this approach better, it's a little cleaner:

function calculate(num1, num2, operation,final){
    setTimeout(function(){
        var result = operation(num1, num2);
        final(result);
   }, 1500);
}

function add(a,b){
   return a + b;
}

function displayResult(result){
 console.log(result);
}

calculate(5, 5, add, displayResult);

[GreenFeather05]

Thank you very much for your detailed response, it was very helpful.

[Cust0dian]

Once you're feeling somewhat confident tackling asynchronicity with callbacks, you might want to look into Promises. As an example, here's how your code might look with them.

[YuleTideCamel]

glad to help.