When to use a function or a var

Posted on 2015-02-05
Last Modified: 2015-02-10

In JavaScript when would you use a var over a function or vice versa?
Or is it just personal preference?


var investment = function(){};
as opposed to
function investment() {};
Question by:Soluga
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LVL 11

Expert Comment

by:Dany Balian
ID: 40590685
Well it has to do with reusability! If u want to use the function al over again then use functions! If it's a one time thing then just type it!

Author Comment

ID: 40590868
Hi Danny,

So would you then use a var to create an instance of the function?
Such as ..

var = investment();

function investement(){};
LVL 33

Assisted Solution

by:Big Monty
Big Monty earned 250 total points
ID: 40591414
if you expect a value to be returned from the function, then it would be better to put it a variable. if not, then just calling the function by name would be the best way to go (purely for readability purposes)
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LVL 11

Accepted Solution

Dany Balian earned 250 total points
ID: 40593032
if you need to use the var many times.. then yes you do that..
instead of doing

if (getproductdiscount()>0) {
total = total + getproductdiscount();
} else {
total = total - getproductdiscount();
in this case getproductdiscount() will be executed and calculated 3 times

var disc=getproductdiscount();
if (disc>0) {
total = total + disc;
} else {
total = total - disc;
will run the function just once
LVL 11

Expert Comment

ID: 40593043
I think this explains the difference between function declarations and function expressions :
LVL 11

Expert Comment

ID: 40600192
It's interesting that you accepted those two comments even though they answer a completely different question.
What they answer is why put the result of a function call in a variable
result = myfunction();
if (result > 0)
    total = total + result;

Open in new window

vs. using directly the result of the function.
if (myfunction() > 0)
    total = total + myfunction();

Open in new window

Your question was about the difference between a function declaration
function investment() {}

Open in new window

and a function expression
var investment = function(){};

Open in new window


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