NodeJS Promise

promise.js

const fs = require('fs');

let createFile = (filename) => {
    return new Promise((resolve, reject) => {
        if (fs.existsSync(file)) {
            reject("File Exists");
        } else {
            fs.appendFile(file, 'Hello World', (error) => {
                if (error) {
                    reject(error);
                } else {
                    resolve("File Created");
                }
            });
        }
    });
}

var file = 'hello.txt';

createFile(file).then((resolve) => {

    console.log(resolve);

}).catch((reject) => {

    console.log("File Creation Failed");
    console.log(reject);

});