NODE JS Harmony ES6 vs ES5

var fs = require('fs');

//ES5 way, callbacks.

fs.readFile(process.argv[2], (error, text) =>
   {
    if(error) {
        console.error("Error");
    } else {
        try {
            var obj = JSON.parse(text);
            console.log(JSON.stringify(obj, null, 4));
        } catch (e) {
            console.error("Invalid JSON file");
        }
    }
})

//Run with "node --harmony [filename] [file.json]"

//ES6 way, creating a promise function, then resolving it with '.then' below.

function getFileContents(file) {
    return new Promise(
        (resolve, reject) => {
            fs.readFile(file, (err, res) => {
                if(err) {
                    reject('Invalid File: ' + new Error(this.statusText));
                } else {
                    try {
                        var obj = JSON.parse(res);
                        var data = JSON.stringify(obj, null, 4);
                        resolve(data);
                    } catch (e){
                        reject("Invalid JSON file")
                    }
                }
            })
        }
    )

}


getFileContents(process.argv[2])
    .then((value) => {
    console.log("value");
    console.log(value);
},
         (reason) => {
    console.log("error");
    console.log(reason);
})