为什么不将变量声明为函数的参数？

Question

I don't see that in any shorthand technique or stackOverflow questions..then I wonder if the following can be a shorthand technique.

Imagine I have a function which I know there is exactly 1 argument that will be passed to it :

function myFunc(arr) {
  var i;
  for(i = 0; i < arr.length; i++ ) {
    if(arr[i] === 3) {return true;}
  }
}

Is it a good practice in that case to write :

function myFunc(arr, i) {
  for(i = 0; i < arr.length; i++ ) {
    if(arr[i] === 3) {return true;}
  }
}

I know that in most case we only save 4 bytes and this represent a very small improvement but sometimes for a short function it can be more readable without wasting 1/2 lines just to declare variables.

Edit: also I want to declare i in the scope of the function and not in the for loop sinc I want to be able to reuse it.

Answer 1

You would only do this if you were going to actually use i in the for loop.

eg:

function myFunc(arr, i) {
    for(i; i < arr.length; i++ ) {
        arr[i];
    }
}

// Why you would do this though, is another matter (and bizarre)
myFunc(anArray, 9); 

Instead, it would be better to do:

function myFunc(arr) {
    for(var i = 0; i < arr.length; i++ ) {
        arr[i];
    }
}

and not worry about 4 bytes...