Hands-On Functional Programming with TypeScript

Trailing commas in function arguments

Trailing commas are commas that are used after the final argument of a function. Using a comma after the last parameter of a function can be useful because it is very common to forget a comma when we modify an existing function by adding additional parameters.

For example, the following function only takes one parameter and doesn't use trailing commas:

function greetWithoutTralingCommas(    name: string): string {    return 'Hi! ${name}';}

Some time after the initial implementation, we might be required to add a parameter to the previous function. A common mistake is to declare the new parameter and forget to add a comma after the first parameter:

function updatedGreetWithoutTralingCommas(    name: string surname: ...