From the book Maintainable JavaScript it mentioned :

```
// Bad: Testing to see if an argument was passed
function doSomething(arg1, arg2, arg3, arg4){
if (arg4 != null){
    doSomethingElse();
  }
}

```

but I feel using `!= null` here is quite effective, it filtered both the case of argument not passed or it is passed as null

any reason why the author suggest it is bad ?