Find/count unique lines (i.e. 'cat filewithduplicates.log | sort | uniq -c | sort -rn')

uniq.js

#!/usr/bin/env node
// $ cat filewithduplicates.log | uniq.js | sort -rn | cut -f 2-

var uniq = {};
require('readline').createInterface({
	input: process.stdin,
	terminal: false
}).on('line', function(line){
	uniq[line] = ++uniq[line] || 1;
}).on('close', function () {
	Object.keys(uniq).forEach(function (key) {
		console.log(uniq[key] + '\t' + key);
	});
});