How do arrow functions work?

Arrow functions in JavaScript are a compact alternative to traditional functions introduced in the ES6 standard, which changed the approach to writing concise and modern code. They have several important syntactic and conceptual features that must be considered when developing programs.

The first aspect is their concise syntax, which significantly reduces the amount of written text. For example, you can omit the parentheses around a single function argument and omit the return keyword if the function body consists of a single expression.

The second and most crucial conceptual point is that arrow functions do not have their own execution context. They always inherit it from the surrounding lexical environment, which completely solves the historical problem of context loss inside array methods or asynchronous timers.

The third feature is that such functions lack the built-in arguments pseudo-array. Instead, modern JavaScript recommends using the rest parameters syntax, which behaves more predictably.

The fourth restriction applies to using arrow functions as object constructors. They cannot be called with the new operator because they completely lack an internal instance creation method and the special prototype property.

In practice, arrow functions are indispensable when passing small callbacks to methods like map, filter, and reduce. However, they should not be used as object methods if dynamic context binding to the calling object via the this keyword is required.