Javascript best practices - where's the best place to define a helper function inside a loop? [closed]

Question

What's a better practice, this:

myArray.forEach(function(item)) {

    doSomething(item);

    function doSomething(an_item) {
        console.log(an_item);   
    }

}

or this:

myArray.forEach(function(item)) {

    doSomething(item);

}

function doSomething(an_item) {
    console.log(an_item);   
}

Does the first example create multiple instances of the function, or does it create it just the first time through the loop?

Thanks for any insight!

Answer 1

myArray.forEach(function(item)) {

    doSomething(item);

}

function doSomething(an_item) {
    console.log(an_item);   
}

this function is best because it will created only one time ;

and

myArray.forEach(function(item)) {

    doSomething(item);

    function doSomething(an_item) {
        console.log(an_item);   
    }

}

is a bad due to every time function will create during loop process

Answer 2

The second. Use the second form (because the first form will slow down your user's experience, which may well be a phone or low powered device), or the even shorter form

myArray.forEach(doSomething);

function doSomething(element, index, array) {
  console.log("myArray[" + index + "] = " + element);
}