class.mdx

Class Interop

new

Use bs.new to emulate e.g. new Date():

typet; [@bs.new] externalcreateDate:unit => t="Date";letdate= createDate();

Output:

vardate=newDate();

You can chain bs.new and bs.module if the JS module you're importing is itself a class:

typet; [@bs.new] [@bs.module] externalbook:unit => t="Book";letbookInstance= book();

Output:

varBook=require("Book");varbookInstance=newBook();

Bind to JS Classes

JS classes are really just JS objects wired up funnily. In general, prefer using the previous object section's features to bind to a JS object.

OCaml having classes really helps with modeling JS classes. Just add a [@bs] to a class type to turn them into a Js.t class:

classtype _rect = [@bs] { [@bs.set] pub height: int; [@bs.set] pub width: int; pub draw: unit => unit };typerect=Js.t(_rect);

For Js.t classes, methods with arrow types are treated as real methods (automatically annotated with [@bs.meth]) while methods with non-arrow types are treated as properties. Adding bs.set to those methods will make them mutable, which enables you to set them using #= later. Dropping the bs.set attribute makes the method/property immutable. Basically like the object section's features.