Getting a JSON matrix of MRT travel times

mrt.sg.js

/* global $ */

function getInputs() {
	return $('#stations-list li').map(function() { 
	    return { 
	        symbol: $(this).data('skey'),
	        name: $(this).text()
	    };
	}).toArray();
}

function getLookup() {
	return getInputs().reduce((acc, data) => {
		acc[data.symbol] = data.name;
		return acc;
	}, {});
}

function throttled(promiseGeneratingFn, batchSize = 100) {
	let count = 0;
	let waitChain = Promise.resolve();
	let promiseQueue = [];

	return (...args) => {
		if (count % batchSize === 0) {
			// awkward, because of the mutable aspect of promiseQueue
			waitChain = (queue => waitChain.then(() => Promise.all(queue)))(promiseQueue);
			promiseQueue = [];
		}

		const tail = waitChain.then(() => promiseGeneratingFn(...args));
		promiseQueue.push(tail);
		count += 1;
		return tail;
	}
}


function tripInfo(from, to) {
  return $.ajax('tripcalc', {
    type: 'POST',
    data: `station_a=${from}&station_b=${to}`
  }).then(msg =>
  	({
  		from, to, duration: /about ([0-9]+) minutes/.exec(msg)[1]
  	})
  );
}

const throttledTripInfo = throttled(tripInfo, 30);

function main() {
	const promises = [];
	const matrix = {};
	const inputs = getInputs();
	const len = inputs.length;

	for (var i = 0; i < len; i += 1) {
		for (var j = 0; j < len; j+= 1) {
			if (i !== j) {
				const station1 = inputs[i].symbol;
				const station2 = inputs[j].symbol;
				promises.push(throttledTripInfo(station1, station2));
			}
		}
	}

	return Promise.all(promises).then(everything => {
		everything.forEach(thing => {
			matrix[thing.from] = matrix[thing.from] || {};
			matrix[thing.from][thing.to] = thing.duration;
		});
		return matrix;
	});
}

main().then(matrix => console.log(matrix));