Ramda-Transducers.js

// Ramda Code : https://cdnjs.cloudflare.com/ajax/libs/ramda/0.24.1/ramda.min.js

// Run the below examples at https://ramdajs.com/repl/

{
	const the_numbers = [1, 2, 3, 4];

	const addOne = R.map(R.add(1));
	const timesTwo = R.map(R.multiply(2));
	const appendToAccum = (acc, val) => R.append(val, acc);

	const leftToRight = R.compose(
		addOne,    // [2,3,4,5]
		timesTwo); // [4,6,8,10] 
	R.transduce(leftToRight, appendToAccum, [], the_numbers);
}

{
	const the_numbers = [1, 2, 3, 4];

	const isOdd = (x) => x % 2 !== 0;
	const addOne = R.map(R.add(1));
	const keepOdd = R.filter(isOdd);
	const timesTwo = R.map(R.multiply(2));
	const takeOne = R.take(1);
	const appendToAccum = (acc, val) => R.append(val, acc);
	const doTap = tap_mess => R.map(x => {console.log(tap_mess, x); return x;});

	const leftToRight = R.compose(
		          doTap('START'),   // [1,2,3,4]
		addOne,   doTap('ADD ONE'), // [2,3,4,5]
		keepOdd,  doTap('ODD'),     // [3,5]
		timesTwo, doTap('TIMES 2'), // [6,10]
		takeOne,  doTap('END'));    // [6] 
	R.transduce(leftToRight, appendToAccum, [], the_numbers);
}