ReasonML Quick Start Guide

Option module

Belt's Option module is a collection of utility functions for working with the option type. For example, to unwrap an option and throw a runtime exception if the option's value is None, we can use getExn:

let foo = Some(3)->Belt.Option.getExn;Js.log(foo); /* 3 */let foo = None->Belt.Option.getExn;Js.log(foo); /* raises getExn exception */

Belt functions that are able to throw runtime exceptions always have the Exn suffix.

An alternative function to unwrap an option that isn't able to throw a runtime exception is getWithDefault:

let foo = None->Belt.Option.getWithDefault(0);Js.log(foo); /* 0 */

The Option module provides several other functions such as isSome, isNone, map, mapWithDefault, and more. Check the documentation for ...