When you're working with Angular, you may have noticed that when you run the build command, it generates output files that end with "es5" and "es2015." You might be wondering why it doesn't use terms like "es6" or no suffix at all. Let's dive into this and clarify why Angular builds create files with these specific suffixes.
Angular, being a popular front-end framework for building web applications, follows specific conventions when it comes to generating optimized output during the build process. By default, Angular uses the TypeScript language, which is a superset of JavaScript. This means that when you write code in Angular, it ultimately gets compiled down to JavaScript code that browsers can understand.
The "es5" and "es2015" suffixes you see in the output files refer to different versions of ECMAScript, which is the standard that JavaScript is based on. ES5 refers to ECMAScript 5, which is an older version of the standard. ES2015, also known as ES6, stands for ECMAScript 2015, which introduced many new features and improvements to JavaScript.
So, why does Angular create both "es5" and "es2015" files? The reason behind this is browser compatibility. Not all browsers fully support ES2015 features, especially older browsers. By generating output files in both ES5 and ES2015 formats, Angular ensures that your application remains compatible with a wide range of browsers. The ES5 files serve as a fallback for older browsers that might not understand the newer ES2015 syntax and features.
As for the absence of "es6" or no suffix at all, it comes down to Angular's approach to optimizing and organizing the build output. While ES6 is a common term used to refer to ECMAScript 2015, Angular chooses to use "es2015" instead to align with the official ECMAScript naming conventions. The decision to omit a suffix altogether is likely a design choice to maintain consistency and clarity in the generated file names.
In conclusion, the use of "es5" and "es2015" suffixes in Angular build output files is a deliberate strategy to ensure cross-browser compatibility and optimize the generated code for different ECMAScript versions. By generating files in both formats, Angular helps developers reach a broader audience without sacrificing the benefits of modern JavaScript features. Understanding these nuances can empower you to make informed decisions and leverage Angular's capabilities effectively in your web development projects.