What is the difference between var foo=function() and function foo()

Question

I have a JavaScript class Test that has a private function foo that looks like this:

function Test(){}
(function()
{
    var foo = function(){
        // do stuff
        console.log('private work');
    }

    this.publicStuff = function(){
        foo();
    }

}).apply(Test);

and one that looks like this

function Test(){}
(function()
{
    function foo(){
        // do stuff
        console.log('private work');
    }

    this.publicStuff = function(){
        foo();
    }

}).apply(Test);

they both work OK and do same stuff and can even coexist like this:

function Test(){}
(function()
{
    var foo = function(){
        // do stuff
        console.log('private work VAR');
    }

    function foo(){
        // do stuff
        console.log('private work FUNC');
    }

    this.publicStuff = function(){
        foo();
    }

}).apply(Test);

But when they are together, the var foo = function() gets executed and the other one not.

What is the difference between the two ways of defining these private functions, what is the best practice and what are the advantages/disadvantages of each aproach

Wrong dupe target. It’s [Why can variable declarations always overwrite function declarations?](http://stackoverflow.com/q/21139719/4642212). — Sebastian Simon, Mar 14 '17 at 13:37
You basically overwrite your own function. function foo gets hoisted, then you overwrite it again with var foo, so only one of the two will work if you give them the same name. — Shilly, Mar 14 '17 at 13:38
[Named function expressions demystified](http://kangax.github.io/nfe/#expr-vs-decl) is an article worth reading — Moritz Roessler, Mar 14 '17 at 13:43
it seems that I wasn't truly aware of JavaScript variable and function hoisting but now I am. Thanks for all you comments. — Bogdan, Mar 14 '17 at 13:53

What is the difference between var foo=function() and function foo()

0 Answers0