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JavaScript

Posted by Nick Ruiz
Nick Ruiz
18,492 Points

named functions vs named variables with functions

Hello all, I'm trying to grasp when I would want to create a named function vs a named variable and assigning it to a function. For example:

var sendAJAX = function(){
  xhr.send();
}

vs

 function sendAJAX(){
     xhr.send();
   }

My past JAVA experiences have followed the second approach but since I been doing the Javascript course on treehouse sometimes I see the teachers create functions as variables. When would I benefit from the first or the second one? Thanks

2 Answers

Thomas Nilsen
Thomas Nilsen
14,957 Points
Thomas Nilsen
Thomas Nilsen
14,957 Points

In addition to what Erik wrote;

If you use the first approach order matters. Meaning if you were to write something like this:

sayHello(); //This would not work

var sayHello = function() {
    console.log('hello');
}

You have to declare the function before you use them.

The second approach, you don't have to think about that. 

sayHello(); //This works

function sayHello() {
    console.log('hello');
}
Erik Nuber
Erik Nuber
20,629 Points
Erik Nuber
Erik Nuber
20,629 Points

Thanks, I forgot about that too! That is definitely important.

Nick Ruiz
Nick Ruiz
18,492 Points

Oh ok thanks guys I can see how they both are virtually the same but yea that's a good call out. If its defined as a variable I would have to declare the variable first otherwise it will generate a runtime error of variable undefined.

Erik Nuber
Erik Nuber
20,629 Points
Erik Nuber
Erik Nuber
20,629 Points

They are virtually the same thing. However, when you declare a variable a function, you can always reassign the variable to something different. This would work with any variable. If you assigned 

var someNum = 4

someNum = 10

In this way assigning a variable to a function it could achieve the same thing. i don't really know why you would ever want to change a function but, here is an example from Eloquent JavaScript. 

var launchMissiles = function(value) {
  missileSystem.launch("now");
};
if (safeMode)
  launchMissiles = function(value) {/* do nothing */};