What is JavaScript for you? It won’t be an exaggeration to say that most modern web, as well as mobile applications, are built with the help of JavaScript. For years, it has been recognized as one of the preferred programming languages and widely used by developers of all levels.

Needless to say that JavaScript language offers a variety of benefits. It is a perfect solution for building websites that work well for both mobile devices and computers because it ensures accessibility via the same code base. It also makes it relatively easy for programmers to implement complex features in apps. Finally, JavaScript offers developers a wide range of advanced frameworks, libraries, and development tools. With that being said, it becomes pretty clear why it was called the most popular language in the tech world.

One more benefit of this language is its relative simplicity in use. Many aspiring developers start with learning JavaScript, which makes sense – it is understandable, popular, and beneficial. However, despite all the benefits, there are still some pitfalls that may come your way as a JavaScript developer.

Top JavaScript Mistakes Among Devs

According to the survey, 41% of JS developers who currently offer their services on the market have less than 5 years of experience in coding. While this article may not be a revelation for programmers with broad experience, it will most certainly come in handy for those of you who are still at the beginning of your career path.

In the list below, we have collected some of the most common mistakes that almost all JS developers make. Read them carefully to make sure you are not making them as well:

1. Semicolons vs. Commas

Expert developers often use semicolons to keep their code readable. That’s where most beginners make the same big mistake – they believe that semicolons can consume additional memory and, thus, harm the product’s performance. Keeping this faulty belief in mind, they often tend to use commas instead of semicolons.

This is the first common mistake you can avoid. Studies show that additional variable declarations and semicolons do not affect the performance or speed of applications. However, they can help keep your code readable and clean. Thus, there are no reasons to avoid using semicolons.

2024 Research

2. Confusing “=” and “==” Operators

The assignment “=” and comparison “==” operators are often confused by beginners. To avoid this mistake, keep in mind when to use each operator:

  • “=” – to assign values to a variable;
  • “==” – to compare the value of a variable conditionally.

3. DOM

Adding, modifying, removing elements, or otherwise manipulating the DOM is pretty easy in JS. However, it should be done efficiently.

Another common mistake made by programmers is inefficient DOM manipulation. For example, one of the such case can be adding multiple elements one at a time – such an approach is expensive, inefficient, and not likely to work well. A better solution would be to use document fragments instead – this will help you boost performance and efficiency at the same time.

4. Not Getting the Most of the + Symbol

In JavaScript, there are two different purposes for the + symbol:

  • To add variables;
  • To concatenate strings.

Often, beginners forget about the multiple purposes of this symbol and, thus, use it inaccurately. This is one more mistake to watch out for.

5. Misunderstanding the “Strict Mode”

Just in case you are wondering what it is in a nutshell, a “strict mode” (which can be used by adding [‘use strict’ ;] at the beginning of your source files) allows you to enforce stricter error handling and parsing on your code at runtime, and to make it more secure.

There are quite a few benefits of the “strict mode,” but many beginners tend to overlook them, which is another typical JS mistake.

6. Using Named Indexes to Define Array Objects

Using JavaScript, developers are required to define array objects with numeric integer indexes. Every individual element of an array has to be assigned a special value. The mistake is that many aspiring JS developers use the wrong (named) indexes instead of numeric integer indexes.

7. Block Level Scope to Define Variables

Unlike many other languages, JavaScript does not allow you to use the block-level scope for defining variables. By making such a mistake in JS, you increase the risk of bringing new bugs to the code.

8. Not Loading the Code before Referencing

JavaScript requires developers to ensure that their code is loaded before referencing. However, many beginners make the same mistake, trying to execute the code without loading it.

9. Using “This” Incorrectly

One more typical mistake is the improper use of the keyword “this.” The biggest problem here is that the value of this keyword can vary in the runtime, depending on the code’s context. To avoid this mistake, a programmer should always keep an eye on the context and keep in mind the different possible meanings of the “this” keyword.

10. Forgetting to Check whether an Object is Undefined

Often, objects in JavaScript are defined as null by default, and, here, many developers make a big mistake by not checking if it is undefined. To avoid this, be sure to check whether an object is undefined before you go to any calculations.

Bottom Line: How To Avoid Common Mistakes?

Almost every JavaScript developer has made some of the JS mistakes specified in this article at some point in his career.

How to avoid making these typical mistakes? The easiest way to avoid them and become a better specialist is by learning from others’ experiences. Of course, there is no way you can ensure an absolute absence of failures in your career. After all, failures and mistakes are what help a beginner to become a better professional. However, by knowing about the most common mistakes, you can minimize the chances of repeating them and develop as a professional much faster. Hopefully, this article will help you! 

Author’s Bio: This article was provided by Sandra Larson – a professional academic writer at Assignmentbro and an expert in the field of programming. Although Sandra has built a career in online academic help, she is also a dedicated JavaScript developer with years of experience. Apart from helping students with their academic matters, Sandra Larson also participates in running the blog at Elizabethanauthors and freelance development projects, and, in this article, she shares the top 10 mistakes most JavaScript developers make.

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