eachline.js - http://stackoverflow.com/q/27090124/89391

eachline.js

#!/usr/bin/env node
// eachline.js - execute some js per line in a file
//
//     $ time eachline.js datasets/1M.ldj > /dev/null
//
//     real    0m25.211s
//     user    0m24.126s
//     sys     0m2.171s

var fs = require('fs'),
    readline = require('readline');
    vm = require('vm');

var args = process.argv.slice(2);

if (args.length < 1) {
    console.log("Usage: eachline.js FILENAME")
    process.exit(code=1)
}

var rd = readline.createInterface({
    input: fs.createReadStream(args[0]),
    output: process.stdout,
    terminal: false
});

var context = vm.createContext({});
var script = vm.createScript('(function (input) { return input.length; })');
var fn = script.runInContext(context);

rd.on('line', function(line) {
    console.log(fn(line));
});