Common JavaScript Programming Mistakes and How to Avoid Them

William Franks
April 10, 2018

Javascript is now the core of almost all web apps today. There now are uncountable JavaScript-based frameworks and libraries for graphics and animation, single page application development, and even server-side JavaScript platforms. Because of its demand, it’s now a skill that every programmer has to master.

At first glance, it might look simple. However, once you actually dig in, you will realize that there are still nuances that are virtually inevitable. If you are planning to learn Java as a developer or already have started in your learning endeavor, here are the most common JavaScript programming mistakes you should avoid.

  1. Using typeof

You must use typeof only if you need to check whether a variable is defined or not. Otherwise, you’ll experience dreadfully inconsistent behavior.

  1. Using “==”rather than “===”

For beginners, this is one of the usual mistakes. The main difference between these symbols is that “==” converts the type while “===” won’t. Generally, you must use “===” or the Strict Equality Operator as it enables more a predictable behavior. Also, it minimizes hard-to-track bugs.

  1. Not maximizing anonymous wrappers

JavaScript has just a function scope; everything else is basically shared in a single global namespace. If you’re tackling larger projects, it can cause bugs that are harder to track.

Using anonymous wrappers will help here. Anonymous functions generally are viewed as values, so they need evaluation before they could be callable.  This keeps name clashes at bay and organizes your code better.

  1. Using “this” incorrectly in a class

For people who started learning Java before JavaScript, this is a usual blocking point. In the Java language, “this” refers to current objects. However, it’s not the case when using JavaScript. In JavaScript, “this” got five different ways to be bound.

  1. Mistakenly Iterating Through Keys of an Object

Many beginners also get slip-ups with this aspect. There are various means to iterate with the specific properties of a particular object. You may use Object.entries, Object.keys, or a for in a loop.

  1. Deleting Semi-Colons

Omitting semi-colons can ruin your code as well as lead to unknown errors. To do away from this, use a linter in order to ensure that semi-colons aren’t forgotten. Also, put the braces right on the same line of the corresponding statement to avoid unwanted behavior.

  1. Memory Leaks

It refers to the memory that’s no longer used by the app. Various languages have various memory management systems. It’s a mistake not to recognize that memory management can actually be handled on the developers’ end. As you write the code, you as the developer can inform the program whether the value is free or occupied.


If you want a solid code and use the power of JavaScript more effectively, you need to understand how JavaScript works. You are sure to experience JavaScript problems if you lack the proper understanding of the concepts and paradigms of this programing language. One way to understand its workings is to familiarize yourself with the subtleties and nuances of JavaScript to improve your productivity and proficiency further.

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