codeEvalStarterFile.js

// challenge description
// sample input - 
// sample output - 

function coolFunction (input) {
	var dataStruct = []; // or {}
	var output = ""; // or 0
	dataStruct = input.split(',');
	output = dataStruct.join(' ');
	return output;
}

var fs  = require("fs");
fs.readFileSync(process.argv[2]).toString().split('\n').forEach(function (line) {
    if (line !== "") { // ignore empty lines        
        console.log(coolFunction(line));
    }
});

I started off using the editor on the codeEval site but I seem to use the same basic pattern and workflow for each challenge. I use the Chrome console to hack and try stuff out. I copy / paste the function that I write in my text editor (TextMate). The pattern is typically breaking each line into an array or object which I then iterate. It uses less memory if I didn't have a function call but the way I've been doing it works well for me. Last year it would have been Python, this year (2014) it's js.