Dev.to

Common JavaScript Mistakes and How to Fix Them

Common JavaScript Mistakes and How to Fix Them JavaScript is a powerful yet quirky language, and even experienced developers make mistakes. Whether you're a beginner or a seasoned coder, avoiding these common pitfalls will save you hours of debugging. In this article, I’ll cover 10 frequent JavaScript mistakes and how to fix them—with practical examples and best practices. Let’s dive in! Table of Contents 1. Using == Instead of === 2. Not Handling undefined or null 3. Modifying Objects While Iterating 4. Ignoring Asynchronous Behavior 5. Memory Leaks with Event Listeners 6. Misusing this in Callbacks 7. Blocking the Event Loop 8. Not Catching Promise Rejections 9. Mutating State Directly (React/Angular/Vue) 10. Overusing var Instead of let/const Final Tips to Avoid JS Mistakes 1. Using == Instead of === The Mistake\ Using loose equality (==) can lead to unexpected type coercion: console.log(5 == "5"); // true (WAT?!) The Fix\ Always use strict equality (===) to compare both value and type: console.log(5 === "5"); // false (correct) 2. Not Handling undefined or null The Mistake\ Assuming a variable exists without checks: function greet(user) { return "Hello, " + user.name; //

Apr 18, 2025 - 17:48
 0
Common JavaScript Mistakes and How to Fix Them

Common JavaScript Mistakes and How to Fix Them

JavaScript is a powerful yet quirky language, and even experienced developers make mistakes. Whether you're a beginner or a seasoned coder, avoiding these common pitfalls will save you hours of debugging.

In this article, I’ll cover 10 frequent JavaScript mistakes and how to fix them—with practical examples and best practices. Let’s dive in!

Table of Contents

  • 1. Using == Instead of ===
  • 2. Not Handling undefined or null
  • 3. Modifying Objects While Iterating
  • 4. Ignoring Asynchronous Behavior
  • 5. Memory Leaks with Event Listeners
  • 6. Misusing this in Callbacks
  • 7. Blocking the Event Loop
  • 8. Not Catching Promise Rejections
  • 9. Mutating State Directly (React/Angular/Vue)
  • 10. Overusing var Instead of let/const
  • Final Tips to Avoid JS Mistakes

1. Using == Instead of ===

The Mistake\
Using loose equality (==) can lead to unexpected type coercion:

console.log(5 == "5"); // true (WAT?!)

The Fix\
Always use strict equality (===) to compare both value and type:

console.log(5 === "5"); // false (correct)

2. Not Handling undefined or null

The Mistake\
Assuming a variable exists without checks:

function greet(user) {  
  return "Hello, " + user.name; //
Read More

Tags:

Previous Article

Apple Leads Samsung in 2025

Next Article

Soplang The Somalia Programming Language

Related Posts

Mesh Gradient with Animation in SwiftUI [Video]

Mesh Gradient with Animation in SwiftUI [Video]

Feb 25, 2025  0

Aula02 da imersao Dev

Aula02 da imersao Dev

Apr 7, 2025  0

Top 5 Benefits of Using a Continuous Integration (CI) System 55542342 title

Top 5 Benefits of Using a Continuous Integration (CI) S...

Apr 4, 2025  0