Bad:

Good:

function hashIt(data) {
  let hash = 0;
  const length = data.length;
    const char = data.charCodeAt(i);
    hash = ((hash << 5) - hash) + char;
    // Convert to 32-bit integer
    hash &= hash;
  }
}

Version control exists for a reason. Leave old code in your history.

Good:

doStuff();

Remember, use version control! There’s no need for dead code, commented code,
and especially journal comments. Use git log to get history!

Bad:

function combine(a, b) {
}

They usually just add noise. Let the functions and variable names along with the
proper indentation and formatting give the visual structure to your code.

Bad:

Good:

$scope.model = {
  menu: 'foo',
  nav: 'bar'
};
const actions = function() {
};