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JavaScript

Posted by Robert Stefanic
Robert Stefanic
35,170 Points

What are the advantages to defining a function as a variable in JavaScript?

So I see people who define their functions as variables in JavaScript. Why would you do this?

So there's this way of defining a function:

function newFunction() { //Code }

and this way:

var newFunction = function() { //Code };

The only difference I can really see is that, in the first example, you can call a function at anytime as long as it's defined somewhere in the document, where as if you wanted to define a function as a variable, like in the second example, it'd need to be defined before you called it -- but why would anyone do that? It just seems like the second method takes longer and is a more complicated way to define a function.

Thanks.

1 Answer

Steven Parker
Steven Parker
243,318 Points
Steven Parker
Steven Parker
243,318 Points

Your observation is true for most simple cases. But there are times when second form is required, such as when a function is defined by calling another function which returns a function. Or the variable being assigned may have a special scope. Or something else about the assignment differs from what a normal function declaration would do.

You'll probably never need to use the second form yourself until you have learned the specific reason for why it is required in the situation you are programming.

In existing code, you'll need to examine each situation to see if it was used by necessity or just the author's preference.

Robert Stefanic
Robert Stefanic
35,170 Points

I see. I don't know if I quite understand the nested example, but I do get the special scope one (like if a function is defined in another function).

For now, I don't see a reason for defining it the second way, and I guess until it comes up, I won't fret about it too much.

Thanks for your reply!