JavaScript’s Best Security Practices

You are reading Part 31 of the 39-part series: JavaScript Skill Progression: The Path from Beginner to Extreme. [Level 5]

Introduction

Security is a critical aspect of JavaScript development. Applications that fail to implement proper security measures are vulnerable to attacks like Cross-Site Scripting (XSS), Cross-Site Request Forgery (CSRF), and SQL Injection. This article explores best practices for securing JavaScript applications and sanitizing user inputs.

1. Cross-Site Scripting (XSS) Prevention

XSS occurs when malicious scripts are injected into web pages, often through user inputs, and executed in the victim’s browser.

How to Prevent XSS:

• Escape and sanitize user inputs:

  function sanitizeInput(input) {
      const temp = document.createElement("div");
      temp.textContent = input;
      return temp.innerHTML;
  }
  let userInput = "<script>alert('XSS')</script>";
  console.log(sanitizeInput(userInput)); // Output: &lt;script&gt;alert('XSS')&lt;/script&gt;
  

• Use Content Security Policy (CSP):

  <meta http-equiv="Content-Security-Policy" content="default-src 'self'; script-src 'self'">
  

• Avoid innerHTML when inserting user input:

  document.getElementById("output").textContent = userInput; // Safe
  

2. Cross-Site Request Forgery (CSRF) Prevention

CSRF tricks users into executing unwanted actions on authenticated websites.

How to Prevent CSRF:

• Use CSRF Tokens:

  fetch('/submit', {
      method: 'POST',
      headers: {
          'X-CSRF-Token': getCSRFToken()
      },
      body: JSON.stringify({ data: "secure" })
  });
  

• Implement SameSite Cookies:

  document.cookie = "session=secureSession; Secure; HttpOnly; SameSite=Strict";
  

• Use authentication headers instead of cookies where possible.

3. SQL Injection Prevention

SQL Injection is a severe attack where an attacker manipulates database queries via user input.

How to Prevent SQL Injection in JavaScript Applications:

• Use Parameterized Queries:

  db.query("SELECT * FROM users WHERE username = ?", [userInput]);
  

• Use ORM frameworks (e.g., Sequelize, Mongoose) to handle queries securely.

• Never concatenate user input directly into SQL queries.

4. Securely Handling User Input

All user input should be treated as untrusted and sanitized.

Best Practices for Sanitizing Input:

• Use input validation with regular expressions:

  function isValidUsername(username) {
      return /^[a-zA-Z0-9_]{3,15}$/.test(username);
  }
  console.log(isValidUsername("user123")); // true
  console.log(isValidUsername("<script>")); // false
  

• Use a library like DOMPurify for input sanitization:

  import DOMPurify from 'dompurify';
  let safeHTML = DOMPurify.sanitize('<script>alert("XSS")</script>');
  console.log(safeHTML); // Output: ""
  

5. Other Best Security Practices

You are reading Part 31 of the 39-part series: JavaScript Skill Progression: The Path from Beginner to Extreme. [Level 5]