Here’s a function to get memory usage fairly accurately:
function getMemoryUsage() {
let total_rss = require('fs').readFileSync("/sys/fs/cgroup/memory/memory.stat", "utf8").split("\n").filter(l => l.startsWith("total_rss"))[0].split(" ")[1];
return Math.round( Number(total_rss) / 1e6 ) - 60;
}
Explained here.