knowthen / ramdatutorial

Companion source code for a Ramda Tutorial

Companion Source for Ramda Tutorial

"What's Ramda?"

Ramda is a Functional Programming library for JavaScript, that is simlar to Lodash and Underscore.

"What's different about Ramda vs. Lodash?"

Ramda follows many Functional Principles such as:

• Functional Purity
• Immutability
• Currying
• Composition

"Ok, big deal! Why should I care?"

There's many reasons, but if I had to give you one, I'd say: It provides a nice, simple way to build sophisticated logic through function composition.

"What's function composition?"

It's a way to create new functions by combining two or more pure functions. I like to think of it as creating new functions without having to add new logic.

"This seems interesting, where can I learn more?"

If Ramda and functional programming looks interesting, and you want to learn more, please consider taking my course "Functional Programming For Beginners with JavaScript"

ramdatutorial's Issues

Slight impurity in `calcScore` function

Hi James, great series, I really enjoyed it. Was just wondering, and correct me if I'm wrong, but doesn't the calcScore function break the "Pure function rules" by relying externally on the constant groupedByProp ? This would need to be handed in as an argument, no?

ramdatutorial/index.js

Lines 39 to 54 in 8132dec

	const groupedByProp = R.reduce(groupByPropReducer, {}, cities);
	// console.log(groupedByProp);
	const calcScore = city => {
	const { cost = 0, internetSpeed = 0 } = city;
	const costPercentile = percentile(groupedByProp.cost, cost);
	const internetSpeedPercentile = percentile(
	groupedByProp.internetSpeed,
	internetSpeed,
	);
	const score =
	100 * (1.0 - costPercentile) +
	20 * internetSpeedPercentile;
	return R.merge(city, { score });
	}