Prefer local variables as parameters

When calling a global variable, the interpretation engine must check that it exists in all the scopes, that it has a value, etc. Passing global variables as arguments gives them the status of local variables inside the function, thus saving computing time (CPU cycles).

CASE 1 (Avoid as possible)

You are back on the service code. You see that the func1() uses globalVariabl1. Okay, but whats its value by now ? How does it change ? Who mutates the globalVariabl1 before it comes to this function ? What have been the sequence of all these mutations ? You would have no idea. It will be quite difficult to figure all this out.

CASE 2 (Recommended)

You are back to you code, and see that the func0() fetches something and then passes it to func1(param1) as a parameter. You clearly know what the data is, how does it gets here.

Noncompliant Code Example

var aGlobal = new String('Hello');

function globalLength(){
    length = aGlobal.length;
    console.log(length);
}

globalLength();

Compliant Solution

var aGlobal = new String('Hello');

function someVarLength(str){
    length = str.length;
    console.log(length);
}

somVarLength(aGlobal);