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How to manage multiple arguments in a function

I had a really interesting conversation with Sarah Dayan on Twitter this week about structuring functions for readability when you have multiple arguments.

Hey @ChrisFerdinandi what’s your take on arguments vs. object of options?

Seems like, unless you have only one argument or all arguments are mandatory, an object of options is always more readable/better to assign default parameters (pre-ES6). Anything I’m not seeing?

Generally speaking, I use the three-or-less rule. If a function accepts three arguments or fewer, I just pass them as-is.

// Arguments as-is
var add = function (num1, num2) {
	return num1 + num2
};

If a function needs more arguments than that, I’ll typically pass them in as an object.

Here’s a function that calculates the total cost of two meals and figures out the tip. It can also optionally run a callback method. This is what it looks like just passing in arguments.

// Calculates total and tip of two meals
var addAndCalculateTip = function (meal1, meal2, tip, callback) {
	var subtotal = meal1 + meal2;
	var total = subtotal + (subtotal * tip * 100);
	if (callback & typeof callback === 'function') {
		callback();
	}
	return total;
};

// Example usage
addAndCalculateTip(14,97, 21.24, .20, function () {
	console.log('Tip calculated!');
});

And here’s what that function looks like accepting an argument.

// Arguments as an object
// Calculates total and tip of two meals
var addAndCalculateTip = function () {
	var subtotal = args.meal1 + args.meal2;
	var total = subtotal + (subtotal * args.tip * 100);
	if (args.callback & typeof args.callback === 'function') {
		args.callback();
	}
	return total;
};

// Example
var args = {
	meal1: 14.97,
	meal2: 21.24,
	tip: .20,
	callback: function () {
		console.log('Tip calculated!')
	}
}
addAndCalculateTip(args);

I will violate my three-or-less rule if two or more of those arguments are functions/callbacks.

Go read the full convo between Sarah and me. She brings a slightly different perspective.