Hands-On Functional Programming with TypeScript

The this operator in the function context

The value of this inside a function depends on how the function is invoked. If we invoke a function in non-strict mode, the value of this within the function will point to the global object:

function f1() {  return this;}f1() === window; // true

The preceding example should be implemented using JavaScript. The preceding code will fail in TypeScript when the strict compilation flag is enabled because it also enables the noImplicitThis flag.

However, if we invoke a function in strict mode, the value of this within the function's body will be undefined:

console.log(this); // global (window)function f2() {  "use strict";  return this; // undefined}console.log(f2()); // undefinedconsole.log(this); // window ...