Issues Plaguing My Asynchronous JavaScript Implementation

Question

Issues Plaguing My Asynchronous JavaScript Implementation

class FileChecker {
    constructor() {
        this.arguments = process.argv.splice(2);
        this.fileToCheck = this.arguments[0];
        this.directoryToSearch = this.arguments[1] ? this.arguments[1] : '';

        this.currentDirectory = process.cwd();
        this.finalDestination = `${this.currentDirectory}\\` + this.directoryToSearch;

        //Issue Area
        if(this.checkIfFileExists(this.fileToCheck, this.finalDestination)) console.log("FILE EXISTS")
        else console.log("FILE DOES NOT EXIST");
    }

    async checkIfFileExists(file, directory) {
        try {
            let files = await fs.readdir(directory);
          
            return files.includes(file);
        } catch(error) {
            console.log("Error: ", error)
            return false;
        }
    }
}

I am attempting to verify the presence of a file in a directory using promises for file system operations. However, the problematic section consistently returns true, and I am running low on solutions.

javascript asynchronous fs

Answer 1

Answer №1

When you use if (this.fileExists...), it is essentially the same as if (true) because this.fileExists always returns a Promise, which is automatically converted to a boolean value of true

Instead, it is recommended to call fileExists with await and wrap this call in an IIFE function

Remember to add a semicolon at the beginning of the IIFE function to prevent concatenation with the previous line (this.destination(async...))

class Main {
  constructor() {
    this.argument = process.argv.splice(2)
    this.fileToCopy = this.argument[0]
    this.destination = this.argument[1] ? this.argument[1] : ''

    this.callAdress = process.cwd()
    this.finalAdress = `${this.callAdress}\\` + this.destination

    ;(async () => {
      if (await this.fileExists(this.fileToCopy, this.finalAdress))
        console.log('EXISTS')
      else console.log('DOESNT EXISTS')
    })()
  }

  async fileExists(file, path) {
    try {
      let files = await fs.readdir(path)

      return files.includes(file)
    } catch (e) {
      console.log('ERROR', e)
      return false
    }
  }
}

Answer 2

When you use if (this.fileExists...), it is essentially the same as if (true) because this.fileExists always returns a Promise, which is automatically converted to a boolean value of true

Instead, it is recommended to call fileExists with await and wrap this call in an IIFE function

Remember to add a semicolon at the beginning of the IIFE function to prevent concatenation with the previous line (this.destination(async...))

class Main {
  constructor() {
    this.argument = process.argv.splice(2)
    this.fileToCopy = this.argument[0]
    this.destination = this.argument[1] ? this.argument[1] : ''

    this.callAdress = process.cwd()
    this.finalAdress = `${this.callAdress}\\` + this.destination

    ;(async () => {
      if (await this.fileExists(this.fileToCopy, this.finalAdress))
        console.log('EXISTS')
      else console.log('DOESNT EXISTS')
    })()
  }

  async fileExists(file, path) {
    try {
      let files = await fs.readdir(path)

      return files.includes(file)
    } catch (e) {
      console.log('ERROR', e)
      return false
    }
  }
}

Issues Plaguing My Asynchronous JavaScript Implementation

Answer №1

Similar questions

What is the best way to ensure an AJAX get-request waits for the page to finish rendering before providing a response?

Discovering all input elements by utilizing nextAll in jQuery

Caching of audio files in React streaming is enabled

How to use Javascript to pause an HTML5 video when closed

Increasing Taxes and Boosting the Overall Cost

Calculating a Price Quote

I am unable to view the map on my webpage. This issue only arises when I apply a CSS style to it

Cloudflare SSL Error 522 Express: Troubleshooting Tips for Res

How to retrieve the outcome of a stored procedure using node.js

Generate a dynamic JSON object using JavaScript and then deliver it back

Issue with xsl:include functionality in a Firefox extension

Using AngularJS to Apply a Class with ng-repeat

How can I trigger an Iframe JavaScript function from within my webpage?

Creating a Custom FlatList Content Container with React Native

What steps do I need to take to adjust this function based on the timezone?

Navigating to Protected Mobile Platform

"Utilizing Trackball controls, camera, and directional Light features in ThreeJS version r69

Deleting outdated files in a temporary uploads directory - NodeJS best practices

Tips on incorporating CKEditor4 wiris MathML formulas into react JS

Ways to sort items in an array according to their attributes