Arrow functions, for very good reasons, are not meant to behave exactly the same way as regular JavaScript functions. Scores.map(score => +(score / maxScore).toFixed(2)) Īt first glance, it may seem like arrow functions can be used or defined in every way a regular JavaScript function can, but that is not true. The following example shows how an arrow function can be used as a callback function, especially with array methods like map(), filter(), reduce(), sort(), etc. However, they are commonly used wherever an anonymous function expression is required - for example, as callback functions. I’ve gotten to use them almost every day since I knew about them, and I guess that goes for most JavaScript developers.Īrrow functions can be used in so many ways as regular JavaScript functions. Personally, I think arrow functions are one of the most awesome syntax additions to the JavaScript language introduced in the ES6 specification - my opinion, by the way. Hacking stuffs Anomalies in JavaScript arrow functions Waweru Mwaura is a software engineer and a life-long learner who specializes in quality engineering.Glad Chinda Follow Full-stack web developer learning new hacks one day at a time. I hope you enjoyed reading this tutorial and until the next one, keep learning! Finally, you wrote tests and integrated CircleCI. You also learned about the different use cases for IIFEs and some of the problems they solve. In this tutorial, you have learned how JavaScript Immediately Invoked Function Expressions (IIFEs) can lead to faster workflows because of immediate invocations. On the popup, select Fastest, then click Set Up Project.ĬircleCI will then run the build job and it should succeed. From the Projects tab, click Set Up Project next to the name of your remote repository. Save your local changes, commit and push them to GitHub. In this code snippet, we are installing necessary dependencies, saving the cache for faster builds, and then executing your tests. On further investigation, you can see that in this snippet: (function myFunc() ĬircleCI creates a virtual environment for pipeline execution. The only difference is that they do not need to wait for invocation. It is also important to understand that IIFEs are functions themselves. This object then gives us access to jQuery functions without cluttering the global namespace. Any code inside the IIFE that uses the object will only refer to jQuery. $(this).text("Number of clicks: " + counter++) īy using jQuery this way, you have access to the $ object. This code snippet shows how IIFE can be used for global variable declaration: // Global variable declaration One of the main uses of these functions is declaring global variables. IIFEs can be used for different purposes. You will also need to install the required dependencies by running this command: npm install Open a terminal and run this command: git clone `Īfter cloning the repository change the directory to the project directory by running: cd iife-JavaScript It contains the code you will be using in your preferred location. These variables are useful in cases where you may need to prevent accidental modifications or changes to important values.Ĭlone the repository for the tutorial. IIFEs can also be used to create private variables. You will have a chance to use this later in the tutorial in the section about closures. You can use an IIFE to create a scope for only jQuery and its methods.Īnother benefit of using IIFEs is performing asynchronous operations such as the setTimeout() method. If you have another module that also imports this object, you may run into some confusion and errors. If you define a variable in an IIFE, it is accessible only directly within the function.įor example, the library jQuery has the object $. In a traditional function, if you create a variable within the function, it is accessible in the global object. IIFEs prevent pollution of the global JS scope. Having a function that behaves that way can be useful in certain situations. Our tutorials are platform-agnostic, but use CircleCI as an example.Īn IIFE (Immediately Invoked Function Expression) is a function that runs the moment it is invoked or called in the JavaScript event loop.
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