A function should only return what’s needed by outside code so that we don’t expose extra stuff that isn’t needed. That’s because the language features both the “==” and “===” operators. It’s all too easy to keep on adding code to a particular function as you work through the logic in your mind. So, it’s more productive to consider code smells not as problems that need to be eliminated, but rather as prompts for further investigation. As we’ve explained, a code smell is not necessarily a bad thing. Code like this exists in real life, making it harder for developers to read it and reason about it. We're a place where coders share, stay up-to-date and grow their careers. 1. Instead, we should return a string with the fruit color as follows: The code above is much cleaner and only returns the fruit color as suggested by the name of the function. They’re easy to read since there isn’t a lot to read. Code smells scream to be refactored. All rules 237; Vulnerability 17; Bug 51; Security Hotspot 34; Code Smell 135; Tags . As a rule of thumb, you can adopt three as the maximum allowed and then work from there, tweaking and experimenting until you find the right number for your project and team. All else being equal, short functions are just easier to deal with. For detecting copied and pasted code, you can use tools like jsinspect and jscpd. Go further and imagine that our code is not four levels deep, but eight or nine. Functions can have too many parameters. For simplicity’s sake, my function just ignores negative numbers. We should also avoid these code smells as we write code to cater to new requirements. You also have the option to opt-out of these cookies. For example, the following variable name is too short: In the code above, x is too short since we have no idea what it means by looking at the variable name. Usually these smells do not crop up right away, rather they accumulate over time as the program evolves (and especially when nobody makes an effort to eradicate them). . SofCheck Inspector A code smell in itself is not a mistake, but a symptom of an underlying issue in your code. We detect 12 types of code smells in 537 releases of five popular JavaScript applications (i.e., express, grunt, bower, less.js, and request) and perform survival analysis, comparing the time until a fault occurrence, in files containing code smells and files without code smells. The rules say that the function should ignore numbers higher than 1000, and throw an error/exception if one or more negative numbers are passed. By investigating the smell, you…. describeFruit = ({ color, size, name }) =>. It's also great that we only need one object parameter and the order doesn't matter. Skip to content. This website uses cookies to improve your experience while you navigate through the website. “Code smells” are pieces of code that do for your eyes what bad smells do for your nostrils, and usually result in erroneous or harder-to-maintain code. This makes using the function easy since there’s less data to handle and not expose extra information that we don’t want to expose. One of the reasons is that there are many types of…. Remember, code smells sometimes can't be removed, but it's good to know that they are there and you know why they are there. It doesn’t change the meaning or remove any information. Roll up your sleeves, prepare your nose, and let’s get started! JavaScript Code Smells. Code Smells go beyond vague programming principles by capturing industry wisdom about how not to design code. In this tutorial, we’ll explore a few of them. In programming, a code smell is a characteristic of a piece of code that indicates there may be deeper problems. I have no doubt that at least half of you will think that I’m wrong about at least half of these. As we grow as developers we strive to write more maintainable code, but on our journey we often times don't know what that looks like yet. Identifiers that are too long are hard to read. The type–converting comparison, as the name makes clear, converts the operands to the same type before making the comparison. Star 0 Fork 0; Equally important are the parameter list and the overall length. Unique rules to find Bugs, Vulnerabilities, Security Hotspots, and Code Smells in your JAVASCRIPT code . All gists Back to GitHub. Functions with too many levels of indentation are likely long, and long functions are also somewhat likely to have many levels. Not all code smells should be “fixed” – sometimes code is perfectly acceptable in its current form. Code formatters can break code into multiple lines automatically. Defining JavaScript Code Smells. Finally, comments are also often used to “deactivate” a part of the code. So, as you can see, the code above contains “a” for structure and, inside it, three nested “ifs.” Sure, it’s just a simple example, but think of it as a proxy for more complex code. The important thing to keep in mind about code smells is that they’re not necessarily a problem. Finally, code duplication is bad. This category only includes cookies that ensures basic functionalities and security features of the website. And the same applies for most smells you’ve seen today. But I’d also agree with those … The trend continues with yet another excess related code smell. If they have too many, it makes the function more complicated when reading it and calling it. Find them and removing or replacing them is very important for the overall quality of the code. For example, if we have the following function: We have getFruitColor function with the size property, which isn’t relevant to the color of the fruit. We can clean this up by passing in an object instead: As we can see, it’s much cleaner. Code that is so long that they don’t fit in the screen probably should be broken into multiple lines. Dec 6, 2015 - This Pin was discovered by Sebastian Brukalo. If it is not possible to view the whole method on your 5" smartphone screen, consider breaking it up into several smaller methods, each doing one precise thing. Smells are structures in code that violate design principles and negatively impact quality [1]. The term was popularised by Kent Beck on WardsWiki in the late 1990s. JavaScript code smells are code smells that can affect JavaScript code. Code smells are patterns in the source code that can adversely influence program comprehension and maintainability of the program in the long term. Carlos is a .NET software developer with experience in both desktop and web development, and he’s now trying his hand at mobile. You've been going along writing your Angular application, and you've now reached a point where you have enough code in…, We could say automation is the whole raison d’être for software development. I'm web developer interested in JavaScript stuff. But what would the problem with long functions be? He has a passion for writing clean and concise code, and he’s interested in practices that help you improve app health, such as code review, automated testing, and continuous build. Code complexity. But opting out of some of these cookies may have an effect on your browsing experience. If you'd like to become skilled at Refactoring, you need to develop your ability to identify Code Smells. Most developers can smell brittle and fragile code a mile away, but it takes time and training to combat against these smells. Let’s take a look at one: Some developers might state that there’s absolutely nothing wrong with the code above, and I’d agree with them. These cookies do not store any personal information. Since many people recommend 20 lines as a useful method size for Java, let’s use half of that. In this article, we’ll look at some code smells of JavaScript functions, including too many parameters, long methods, identifier length, returning too much data, and long lines of code. I’ve first learned about code smells by reading a post on Coding Horror. Code formatters can rearrange the lines so that they’re shorter in most cases. Fard et al. In this article, we’ll look at some code smells of JavaScript functions, including too many parameters, long methods, identifier length, returning too much data, and long lines of code. That might be somewhat of a subjective matter—not entirely, as you’ll see soon. In this post, we’ve covered seven code smells that might affect your JavaScript codebases. DEV Community © 2016 - 2020. Change Preventers. Since we’re talking about JavaScript here, which is a dynamic language, the “proper” number will likely be less than it would be for a static language such as Java. Be aware of all of them when writing JavaScript, and your code will change for the best. Identifiers that are too short are also a problem. In the post, Jeff Atwood calls code smells “warning signs in your own code.” That’s not that different from how Wikipedia defines them: your own Pins on Pinterest That renders them not only useless but harmful since lying documentation is worse than no documentation at all. Divergent Change. JavaScript, very few studies have investigated code smells in JavaScript applications, and to the best of our knowledge, there is no work that examines the impact of code smells on the fault-proneness of JavaScript applications. 5 parameters are probably the maximum that should be in a function. This item, on the other hand, is as objective as it can get, since it involves an actual metric. We propose a set of 13 JavaScript code smells, collected from various developer resources. In some scenarios, there might be no next steps. Code smells are signs that something is wrong with your code and demands your attention. Each line of code shouldn’t be more 100 characters so that they can be read without scrolling on any screen. Uses the simplest possible way to do its job and contains no dead code Here’s a list of code smells to watch out for in methods, in order of priority. This post has a pretty straightforward structure: it starts by quickly defining JavaScript code smells (and smells in general) with a little more depth. The post JavaScript Clean Code — Smells … So, not really a lot to say here, except “don’t copy and paste code” blindly, without understanding what it does and how it works. Then again: how long is “long?” That’s going to depend on several factors, including the language. Typically, the ideal method: 1. As developers, we seek to employ automation in…, Being a beginner in software testing might feel overwhelming. Too many of them are also a bad sign, and the reasons are pretty much the same as in the previous items. Imagine that, at the deepest level (inside the innermost “if”) we had, instead of a single line, 50. They’re probably there for a reason. Here’s a quick line-up of some smelly jQuery code! We present a JavaScript … It’s a subjective characteristic used for judgment of whether the code is decent quality or not by looking at it. right! The second item in the list is closely related to the previous one, and it makes sense. In this post, we want to help you write better JavaScript, not via tools, but by following some best practices. Lines of code that are too long make the codebase hard to read, understand and debug. Checks style, quality, dependencies, security and bugs. But there are times when there are next steps available, and there are tools that can help you there. Without further delay, let’s go through our list of smells, explaining why they might be symptoms of deeper problems and what you should do about them if anything. It might surprise you to see “comments” as an item in our code smell list, but it sure is. This post was cross-posted to my personal blog. To perform a strict comparison, you should use the identity operator (===) . Is clearly and appropriately named 2. When you’re several levels deep, it becomes harder and harder to reason about the code, keeping track of variables’ values and results of conditions. So, instead of commenting the code, you should strive to refactor into in order to make it easier to understand. Necessary cookies are absolutely essential for the website to function properly. It’s a subjective characteristic used for judgment of whether the code is decent quality or not by looking at it. Performing equality comparisons in JavaScript can be tricky, especially for those who come from other languages. We present a JavaScript code smell … Unused code Paper A. Milani Fard, A. Mesbah, "JSNose: Detecting JavaScript Code Smells” , 13th IEEE International Conference on Source Code Analysis and Manipulation (SCAM 2013), Eindhoven, The Netherlands, 2013 Tôi là Duyệt JavaScript Code Smells Having too many parameters in a method makes passing in data hard since it’s easy to miss some items. A strict comparison is true when the operands have the same type, and the values are equal. The first thing you should check in a method is its name. Since we all use version control nowadays—right? Functions with too many parameters are harder to read, understand, and troubleshoot. In this post, we want to analyze JavaScript code smells. How many levels of indentation should you strive for? As a consequence, they’re easier to troubleshoot, since there’s isn’t a lot of code in which a bug can be hiding. They frequently get out of sync with the code they’re supposed to document. For parameters, I would even argue 'rule of 3' applies here and then for expressiveness, destruct the object args inline, i.e. What happens is that many developers use the version with the two equal signs in situations when they should use the other. This post was written by Carlos Schults. This will also let you assign defaults expressively (one place for someone to see where/if/what defaults assigned for missing args). Mercilessly delete dead code from your codebase, and don’t be sorry about it. GitHub Gist: instantly share code, notes, and snippets. Comments are also often used to explain a piece of code that is too complex. We’re done defining JavaScript code smells. The goal is to create a function that receives a string containing a list of numbers separated by a comma and then calculates their sum. Subscribe to my email list now at http://jauyeung.net/subscribe/, Follow me on Twitter at https://twitter.com/AuMayeung, Many more articles at https://medium.com/@hohanga, Even more articles at http://thewebdev.info/. We also use third-party cookies that help us analyze and understand how you use this website. In other words, code smells are not synonymous with anti-patterns. Instead, they are signs that something might be wrong with your code. In this session we will discuss various common smelly code snippets and discuss techniques on how we can eliminate and protect against their pungent odors creeping into your codebase. So, even though long functions are generally a bad sign, your particular project might have legitimate reasons for having some long functions. Consider the line of code below: The result of that comparison is true, which might seem odd for developers who aren’t used to JavaScript. What are the next steps? If they can be shorter without losing any information then make them shorter. I’ve just been flicking through some slides on “Javascript Code Smells” from Elijah Manor’s blog post and picked up a few tips I’m going to keep in mind and thought I’d share. Now it’s easier to understand what happens in the line above: the equality operator (==) performs a type-converting comparison. Made with love and Ruby on Rails. Code smells occur when code is not written using fundamental standards. Besides, functions with more parameters are more likely to be longer and more complex. SideCI Static code analysis based automated code review tool for Ruby, Python, PHP, JavaScript, CoffeeScript and Go. It also makes the method signature excessively long. OK, but how much is too much? Start with ten lines and change that as you see fit. Finally, long lines of code should be broken into multiple lines so that they’re easier to read and change. Program development becomes much more complicated and expensive as a result. Here we’re talking about function parameters. We strive for transparency and don't collect excess data. In programming, a code smell is a characteristic of a piece of code that indicates there may be deeper problems. Code smells, or bad smells in code, refer to symptoms in code that may indicate deeper problems. A static code analysis solution for PHP, Java and Node.js with many integration options for the automated detection of complex security vulnerabilities. They’re a diagnostic tool used when considering refactoring software to improve its design. The majority of a programmer's time is spent reading code rather than writing code. There are various types of code smells. Doing so is an example of Cargo Cult Programming, which basically means doing things without understanding them. Functions that return data we don’t need isn’t good. Great article! This paper aims to fill this gap in the literature. Study a collection of important Code Smells and compare each one to … Also, code with too many levels stretches horizontally, making it hard to read on mobile devices, on smaller screens, and also when splitting screens (when performing a code review, for instance.). It should stand to reason that copying and pasting code, then changing it a little bit, isn’t a good development practice, even if you don’t know the term code smell. What exactly do we mean by that, and why is it a problem? Also, it shouldn’t be so short that we don’t get enough information from the identifier. Removing code smell is an important task and can be done using automated code review tools. But what are code smells? It also fits better on the screen since it’s shorter. Code smells are signs that something is wrong with your code and demands your attention. Here are some of the bad smells in Java code. Then, it proceeds to cover the smells themselves, with explanation and, when applicable, code examples. Determining what is and is not a code smell is subjective, and varies by language, developer, and development methodology. Is no longer than 30 lines and doesn’t take more than 5 parameters 3. Academia.edu is a platform for academics to share research papers. Identifiers should just be long enough to identify the information we need. For example, we can shorten the following variable declaration: by removing the Of and A to make it shorter. proposed JavaScript code smells detection tool called JSNose [4], which detects 13 types of code smells in JavaScript applications and is referenced in other related studies [28,29]. We start our list with a smell that applies to virtually all programming languages: too many indentation levels. Destructuring and default parameters are great features that we should use wherever we can. Some of the smells are JavaScript specific, while others apply to any language. Fowler’s book is an excellent resource that helps us identify some common code smells and eliminate them. Templates let you quickly answer FAQs or store snippets for re-use. Javascript Code Smells Introduction. The first step is to be aware of them, and we’ve just helped with that. By investigating the smell, you can find and (hopefully) fix its underlying cause, improving your code in the process. We don’t have to worry about passing in many arguments. A function should only return the items that we need and no more. These cookies will be stored in your browser only with your consent. Also, it might make testing harder, since it increases the number of minimum test cases you’d need to test the function. Parallel Inheritance Hierarchies. I’ve first learned about code smells by reading a post on Coding Horror. We look at feature envy and intimate classesContinue reading on Better Programming » Bloaters are code, methods and classes that have increased to such gargantuan proportions that they are hard to work with. JavaScript code smells are code smells that can affect JavaScript code. So that we know the variable is the color of a fruit. For most of the other smells, you should definitely employ a linter, which can help you automate many types of code quality checks. Functions are just easier to read should also avoid these code smells hard since it ’ s to. Tutorial, we seek to employ automation in…, being a beginner in software testing might feel.. Read, understand and debug of some smelly jQuery code you quickly answer FAQs or store snippets for re-use refactor! Re easier to understand what happens in the list is closely related to the previous one and... Since it ’ s a quick line-up of some of the entity that we define come other... See soon information then make them shorter without scrolling on any screen following variable declaration by... Resource that helps us identify some common code smells by reading a on. The important thing to keep on adding code to a particular function as you ’ ll see soon software..., making it harder for developers to read and change that as you see fit as an item in code. S easier to deal with can be tricky, especially for those who come from other languages category includes! Only with your consent documentation is worse than no documentation at all various resources... It a problem maintain and debug true when the operands to the same results wrong your! Keep in mind about code smells are code smells are code smells is that many developers use the with! For example, we ’ ll explore a few of them when writing,... Post on Coding Horror all else being equal, short functions are also often used to explain piece. Is closely related to the same results project might have legitimate reasons for having some functions. Javascript codebases cookies on your website should strive to refactor into in to... Sake, my function just ignores negative numbers pasted code, we ideally. Declaration: by removing the of and a to make it shorter code formatters can break code into multiple automatically... Assign defaults expressively ( one place for someone to see “ comments ” as an item in the source of. Of and a to make this easier to understand why that happens you. With more parameters are probably the maximum that should be broken into multiple lines on factors! Refer to symptoms in code that indicates there may be deeper problems depend on factors... On Pinterest code smells that might affect your JavaScript codebases something might somewhat! Affect your JavaScript codebases essential for the overall quality of the reasons is they. All of them, and it makes sense the overall length identity operator ===. With ten lines and change ; security Hotspot 34 ; code smell an. And development methodology on adding code to cater to new requirements change that as work. It also fits better on the screen since it ’ s going to depend several. Investigating the smell, you can find and ( hopefully ) fix its underlying cause improving... Are times when there are next steps available, and it makes sense are tools that affect! Reading code rather than writing code understand, and the overall length type before the. The important thing to keep on adding code to cater to new requirements s to. By Kent Beck on WardsWiki in the late 1990s two equal signs in when. Code from your codebase, and your code and demands your attention to explain piece! A type-converting comparison is worse than no documentation at all and expensive as a result we for. Applicable, code smell is any symptom in the literature, it proceeds to cover the smells themselves with... Since lying documentation is worse than no documentation at all type less and get the same type and., the following variable declaration: by removing the of and a to make easier! Are equal complexity is harder to read replacing them is very important for the.! And “ === ” operators of Cargo Cult programming, which basically doing... It sure is in both desktop and web development, and your code and demands your attention might feel.! Least half of that these code smells, collected from various developer resources clear... Surprise you to see “ comments ” as an item in our is! Easy to miss some items, being a beginner in software testing might feel overwhelming explain! About passing in many arguments spent reading code rather than writing code to analyze JavaScript code smells are synonymous! Many levels of indentation are likely long, and it makes sense automation in…, being a in. N'T collect excess data degree of subjectivity complicated and expensive as a.!, especially for those who come from other languages while you navigate through the logic your! Let ’ s a quick line-up of some of these cookies will be stored in your mind subjective characteristic for... Industry wisdom about how not to design code is spent reading code rather than code... Long is “ long? ” that ’ s shorter a code smell is necessarily! Code smells as we write code to a particular function as you see fit corner cases to avoid.... Reading code rather than writing code it and calling it are the parameter and... For example, we can see, it ’ s because the.. Equal, short functions are just easier to understand what happens in the line:... Is spent reading code rather than writing code that speaks for itself and can be shorter losing! Who come from other languages that return data we don ’ t all! Other hand, is as objective as it can get, since it involves an actual.! Makes the function more complicated when reading it and reason about and troubleshoot cater new! Step is to be aware of all of them necessary cookies are absolutely essential for website. On several factors, including the language Bug 51 ; security Hotspot ;! Understand what happens in the list is closely related to the previous items to... Learned about code smells browsing experience affect JavaScript code smells ve just with... Quick line-up of some of the code subjective, and your code in some way make! Current form analysis based automated code review tools that something might be no next steps,. Probably should be in a method makes passing in many arguments our list with a that... Rules 237 ; Vulnerability 17 ; Bug 51 ; security Hotspot 34 ; smell. In data hard since it ’ s much cleaner tool for Ruby,,... Of you will think that i ’ ve first learned about code smells are signs something. That demands your attention symptom in the list is closely related to the previous three items have all something do... Be no next steps available, and snippets anti-patterns. instead, they are signs that something wrong. Prepare your nose, and the same as in the literature them, and there are types... A platform for academics to share research papers some long functions be be stored in your browser with... One object parameter and the same results for Java, let ’ s because the language features both “. Takes time and training to code smells javascript against these smells levels deep, but eight or nine explore. The information we need and no more something might be harmless code smells javascript but by following some best practices related smell! Too short don ’ t get enough information from the identifier JavaScript CoffeeScript! We type less and get the same type, and your code the identifier post Coding. Parameter list and the values are equal may indicate deeper problems with parameters..., functions with too many parameters in a method is its name your ability to identify code smells are smells. Fill this gap in the literature why that happens, you need develop... Capture all the meaning of the code, notes, and he’s now trying his hand at.! Most cases you there FAQs or store snippets for re-use or store snippets for re-use parameters are harder read. Need one object parameter and the order does n't matter can get, since it ’ s.! Even though long functions are just easier to read should only return the that... Cookies are absolutely essential for the overall quality of the code subjective characteristic for! One object parameter and the order does n't matter there isn ’ t need ’! Speaks for itself doing things without understanding them help you write better JavaScript, and by. Bear in mind that JavaScript features strict and type–converting comparisons up the code they ’ re not necessarily bad! Developers, we ’ ve seen today to procure user consent prior to running these cookies will be stored your. Pinterest code smells are code smells by reading a post on Coding Horror items we... And debug people recommend 20 lines as a useful method size for Java, let ’ s easier read! Characteristic of a piece of code that speaks for itself to keep mind! Python, PHP, JavaScript, and why is it a problem life, it... Expressively ( one place for someone to see “ comments ” as an item in our code smell 135 Tags. Without losing any information Cult programming, which basically means doing things without understanding them keep... While others apply to any language seen today, quality, dependencies, security bugs. All the meaning of the code get enough information from the identifier present JavaScript! Might surprise you to see where/if/what defaults assigned for missing args ) harder to,.