Hands-On Functional Programming with TypeScript

Composition

Functional composition is a technique or pattern that allows us to combine multiple functions to create a more complex function.

The following code snippet declares two simple functions:

const trim = (s: string) => s.trim();const capitalize = (s: string) => s.toUpperCase();

That two simple functions declared by the preceding code snippet are the following:

• A function used to trim a string
• A function used to transform a piece of text into uppercase

We can create a function that performs both of the preceding operations by composing them as follows:

const trimAndCapitalize = (s: string) => capitalize(trim(s));

trimAndCapitalize is a function that invokes the trim function (using s as its argument) and passes its return to the ...