Hands-On Functional Programming with TypeScript

Lambda expressions

Lambda expressions are just expressions that can be used to declare anonymous functions (functions without a name). Before the ES6 specification, the only way to assign a function as a value to a variable was to use a function expression:

const log = function(arg: any) { console.log(arg); };

The ES6 specification introduced the arrow function syntax:

const log = (arg: any) => console.log(arg);

Please refer to Chapter 2, Mastering Functions, Chapter 4, The Runtime – The Event Loop and the this Operator, and Chapter 5, The Runtime – Closures and Prototypes, to learn more about arrow functions and function expressions.