Question

Just a quick one…

what’s the correct way to format a javascript function?

I see it like this:

function doThis(){
}

and like this:

doThis = function(){
}

Or maybe it make no difference. Please let me know whats best or if they both have different rasons or purposes.

Cheers

C

Answer 1

They are two different things, although they both create a function (and assign it to a variable).

function name () {
}

Is a function-statement (or “function declaration”). It is only legal to appear as a top-level script element or directly as an element of a function: that is, it is not legal for a function-statement to appear inside an if, or while, etc. All function statements are “lifted” to the top of the function (or script), thus the following is valid:

a()
function a () { alert("a") }

In the form:

variable = function name () {} // or variable = function () {}

The function keyword is in a function-expression context: it creates a new function-object and the resulting function-object (just a “normal value”) is assigned to variable. The following is not valid because function-expressions are not lifted.

var b
b() // oops, does not evaluate to a function-object yet!
b = function b () { alert("b") }

All that being said, the “correct way” is to use the function-statement (“function declaration”) form unless there is reason to do otherwise.

Happy coding.

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See also:

• What is the difference between a function expression vs declaration in JavaScript?
• Function Declarations vs. Function Expressions