Unable to delete a file with nodejs in protractor - node.js

Question

I'm trying to delete the file with nodejs fs and I notice that file has been generated then trying to delete (failed to delete the file) while the file is not even uploaded on browser with protractor. Generate and delete file functions are created using nodejs fs.
So how can I put them in a way then wait until file is uploaded then delete the file?
helper.generateFile(filePath);
helper.uploadFile(UploadButtonElement, filePath);
uploadButtonElm.click();
helper.deleteFile(filePath);
Is there a way to execute deleteFile only when below two actions are completed.
helper.uploadFile(UploadButtonElement, filePath);
uploadButtonElm.click();
Thanks.

Answer 1

Protractor operations schedule promises to do things. They do not actually do them. Thus, your helper functions will end up running well before any of the protractor code actually accomplishes what you asked. Use then to chain your dependencies explicitly. Like so:
helper.generateFile(filePath);
helper.uploadFile(UploadButtonElement, filePath);
uploadButtonElm.click().then(function() {
helper.deleteFile(filePath);
});
Please read https://github.com/angular/protractor/blob/master/docs/control-flow.md and https://code.google.com/p/selenium/wiki/WebDriverJs#Understanding_the_API

Answer 2

function deleteAlreadyDownloadedFiles(extension,username) {
    let os = require('os');
    console.log('USERNAME HERE IS'+require("os").userInfo().username);
    var downloadDirectory = '/Users/'+require("os").userInfo().username+'/Downloads/';
    const fs = require('fs');
    const path = require('path');
    const directory = '/Users/'+require("os").userInfo().username+'/Downloads/';
    fs.readdir(directory, (err, files) => {
        if (err) throw err;
         for (const file of files) {
            fs.unlink(path.join(directory, file), err => {
                if (err
                    && (err.code === "EACCES" || err.code === "EPERM")) {
                    console.log("Retrying rename file: ")
                    return;
                }
            });
        }
    });
}